CN108267590B

CN108267590B - PEG (polyethylene glycol) combination number detection method of PEG modified protein

Info

Publication number: CN108267590B
Application number: CN201611270257.4A
Authority: CN
Inventors: 马永; 颜莎; 王俊
Original assignee: ZONHON BIOPHARMA INSTITUTE Inc
Current assignee: ZONHON BIOPHARMA INSTITUTE Inc
Priority date: 2016-12-31
Filing date: 2016-12-31
Publication date: 2021-05-11
Anticipated expiration: 2036-12-31
Also published as: CN108267590A

Abstract

The invention relates to a PEG binding number detection method of PEG modified protein, which comprises the following steps: and (3) after the PEG modified protein sample to be detected is treated, releasing all PEG, detecting the quality of the PEG, and calculating the PEG binding number in the PEG modified protein according to the molar ratio of the protein to the PEG. The method is suitable for different protein types and different PEG modifier types, in particular to PEG modified protein with complex three-dimensional structure, large molecular weight and large steric hindrance, and the PEG binding number is difficult to accurately analyze by other existing methods. In addition, the method has simple operation and good repeatability, and can accurately analyze the PEG binding number of the PEG modified protein.

Description

PEG (polyethylene glycol) combination number detection method of PEG modified protein

Technical Field

The invention relates to the field of drug analysis, in particular to a PEG (polyethylene glycol) combination number detection method of PEG modified protein.

Background

The pharmaceutical proteins and polypeptides generally have the defects of poor biological stability, short in-vivo half-life, immunogenicity and the like, and are generally modified by means of genetic engineering modification, chemical modification and the like so as to overcome the defects. Polyethylene glycol (PEG) is a linear, uncharged polymer that curls freely in solution, with no toxicity, weak antigenicity and good biocompatibility. The covalent modification of protein can increase the in vivo circulation half-life of protein, reduce its antigenicity, increase the solubility of protein and change the biological distribution of protein in human body. Since the modification of proteins with PEG was first reported by Abuchowski, Davis (J.biol.chem.1977,252: 3578-.

Because the protein has more sites which can be modified by PEG, the average modification rate or the PEG combination number of the protein modification degree by PEG is reflected, and the PEG-modified protein has important significance for the research of the structure-activity relationship of the medicaments and the quality control.

The detection method of the PEG binding number of the modified protein drug comprises the following steps: trinitrobenzene sulfonic acid method (TNBS method), fluorescence amine method, nuclear magnetic resonance, Capillary Electrophoresis (CE), matrix assisted laser scanning system (MALDI-MS), Fourier transform infrared spectroscopy (FTIR), Raman scattering spectroscopy, and the like. According to the simplicity and easy operability of the method, the trinitrobenzene sulfonic acid method (TNBS method) and the fluorescence amine method are commonly used, and the principle of the method is to reverse the PEG binding number of the protein by detecting the number of free amino groups. However, for PEG with a complex three-dimensional structure, a large molecular weight and a large steric hindrance, it is difficult for TNBS and fluorescence amine methods to bind to free amino groups wrapped inside a protein higher structure, and thus PEG binding number cannot be accurately analyzed and detected.

Disclosure of Invention

In order to overcome the technical problems, the invention provides a method for accurately detecting the PEG binding number in polyethylene glycol modified protein.

The method for detecting the PEG combination number in the PEG modified protein directly detects the amount of PEG in the PEG modified protein to determine the PEG combination number, and comprises the following steps: the method comprises the steps of processing a sample to be detected, measuring and calculating the content of free PEG in the processed sample, and calculating the PEG binding number in the PEG modified protein according to the content of the free PEG.

The step of processing the sample to be detected is to completely release PEG in the PEG modified protein drug from the protein drug molecules. The released PEG can be free of any polypeptide or amino acid, and can be connected with the polypeptide or amino acid.

Preferably, the step of processing the sample to be tested is to hydrolyze the protein drug into polypeptide or amino acid by using a proteolysis method, the protease is pepsin, trypsin, chymotrypsin or elastase, and is not limited to the trypsin used in the examples.

More preferably, the step of processing the sample to be tested is to destroy the higher structure of the PEG modified protein by high temperature, and then hydrolyze the protein into polypeptide or amino acid by protease, so as to release the PEG combined with the protein.

The inventors have tried other methods, such as acid-base hydrolysis, heating, etc., to achieve the goal of releasing PEG from the protein molecule completely. The sample treatment of the present invention is not limited to the above method, and any method known to those skilled in the art that can completely release PEG from protein molecules can be used for the sample treatment of the present invention.

Preferably, the step of measuring the content of free PEG in the treated sample may be performed by ammonium ferrocyanide-chloroform two-phase system method, 3202 polyethylene glycol residue measurement method as general rule of the fourth pharmacopoeia of china, or SDS-PAGE electrophoresis method.

The SDS-PAGE electrophoresis method is to carry out SDS-PAGE electrophoresis on the treated sample and PEG reference substance gradient solution, and dye after the electrophoresis is finished; quantitatively measuring and calculating the gray value of the dyed lane by using a quantitative analysis system; and determining a standard curve of the concentration and the gray value of the PEG reference substance gradient solution, substituting the data of the gray value quantitatively calculated by the dyed lanes of the processed sample into the standard curve, and converting the content of the free PEG in the processed sample.

Preferably, the dyeing method of the present invention is preferably an iodine dyeing method, wherein the band is dyed because barium ions are combined with polyethylene glycol molecules to form a soluble oxonium ion complex, and then the complex is combined with iodine ions to form an insoluble precipitate. However, the method of staining after SDS-PAGE of the present invention is not limited thereto, and any method capable of developing PEG color may be used in the present invention, for example, a method of developing color with ferric thiocyanate, or a method of developing color with boric acid added to iodine solution.

Preferably, the quantitative analysis process of the stained lanes is performed by using Quantity One software, but the quantitative analysis method of the present invention is not limited thereto, and other quantitative analysis methods of SDS-PAGE electrophoresis bands can be used in the present invention, such as a gel imager, etc.

Preferably, the method for detecting the PEG binding number in the PEG modified protein comprises the following specific steps:

preparation of a test solution: taking a certain amount of test solution with known PEG modified protein content, performing high temperature treatment, adding pancreatin solution, and performing enzymolysis in water bath for later use.

Preparation of PEG standard gradient solution: accurately weighing PEG powder identical to the sample to be detected, adding water to dissolve, preparing PEG standard solution with predetermined content, mixing, and standing. And respectively adding PEG standard substance solutions with different volumes at certain intervals into purified water to prepare gradient concentration solutions with the same final volume, and uniformly mixing to obtain the standard substance gradient solution.

Preparation and loading of samples: and taking the standard substance gradient solution and the test substance solution respectively, carrying out SDS-PAGE electrophoresis experiment, and taking a picture after developing color by an iodine staining method.

Data determination and calculation: quantitatively measuring and calculating the gray value of each dyed lane by using Quantity One 4.4.0 software on the photo; drawing a standard curve of the concentration and the gray value of the PEG standard substance according to the corresponding concentration of the gray value of the staining lane of the PEG standard substance gradient solution; and substituting the gray value of the corresponding dyed lane of the test solution into the standard curve, and calculating to obtain the content of all free PEG in the test solution.

The ammonium iron thiocyanate-chloroform two-phase system method is that the treated sample and PEG reference substance gradient solution are added into the ammonium iron thiocyanate-chloroform two-phase system; measuring the absorbance value of the chloroform phase solution at the wavelength of 510 nm; and determining a standard curve of the concentration and the absorbance value of the PEG reference substance gradient solution, substituting the absorbance value of the treated sample into the standard curve, and converting the content of free PEG in the treated sample.

The 3202 polyethylene glycol residue determination method in the fourth pharmacopoeia of China is to sequentially add a high chloric acid solution, a barium chloride solution and an iodine solution into a treated sample and a PEG reference substance gradient solution; after the mixture is uniformly mixed and reacted for a certain time, measuring the absorbance value at the wavelength of 535 nm; and determining a standard curve of the concentration and the absorbance value of the PEG reference substance gradient solution, substituting the absorbance value of the treated sample into the standard curve, and converting the content of free PEG in the treated sample.

Calculation of the number of PEG-conjugates: calculating the PEG binding number according to the above results, and the calculation formula is as follows:

the method is suitable for different protein types and different PEG modifier types, in particular to PEG modified protein with complex three-dimensional structure, large molecular weight and large steric hindrance, and the PEG binding number is difficult to accurately analyze by other existing methods. In addition, the method has simple operation and good repeatability, and can accurately analyze the PEG binding number of the PEG modified protein.

Drawings

FIG. 1 comparative example 3PEG content-absorbance standard curve

FIG. 2 the method of example 1 of FIG. 2, in which the PEG binding numbers of different batches of PEG site-directed modification asparaginase are detected, the serial numbers 1-6 are standard gradient solutions, 7-9 are three different batches of PEG-ASP double-modification sample solutions, and the serial number 10 is blank

FIG. 3 method of example 2 for detecting PEG binding number of PEG randomly modified asparaginase in different batches

FIG. 4 detection of PEG-ADI PEG conjugation number by the method of example 3

Detailed Description

The terms used in the present invention are explained as follows:

PEG site-directed modification of asparaginase: see patent application No. 201410837456.3, example 1, preparation 1. Each asparaginase molecule can be combined with one, two or three polyethylene glycols which are respectively named as PEG-ASP single modification, PEG-ASP double modification and PEG-ASP triple modification. The PEG modifier used was Y-PALD-40K (available from Xiamen Sonobang science and technology Co., Ltd.): the molecular weight is 40KD, and the compound is formed by connecting two linear methoxy polyethylene glycol derivatives to a central core, and the chemical structural formula is as follows:

PEG randomly modified asparaginase: see patent application No. 201410837460.X example 1 preparation 1. The theoretical value of the PEG binding number of PEG randomly modified asparaginase is between 17 and 25. The PEG modifier used was M-SPA-5000 (available from Kyoto technologies, Inc.).

PEG site-directed modified arginine deiminase: PEG-ADI, two polyethylene glycols can be attached to each arginine deiminase molecule, named PEG-ADI double-repair. The preparation method comprises the following steps:

1. modification reaction:

concentrating the purified ADI protein sample, and replacing modified buffer solution (the mixture ratio is 100mM acetic acid-sodium acetate, pH5.0) with the concentration of about 5 mg/ml; according to ADI PEG: reducing agent molar ratio 1: 4: 600 weighing PEG and reducing agent. The modification reaction is carried out at 4 ℃ for 12-20 hours. Selecting Novel-2-arm-40K (purchased from Xiamen Nobangg science and technology Co., Ltd.) as a modifier, and using sodium borohydride hydride (purchased from sigma) as a reducing agent;

2. modified sample purification

The chromatographic conditions are as follows: the mobile phase A was 20mM PB (pH7.2) and the mobile phase B was 20mM PB containing 1M NaCl (pH 7.2).

Loading: diluting the modified reaction product by 10 times with solution A, diluting by 5 times with double distilled water, loading 10ml/min, and binding to anion exchange column (purchased from GE, Q sepharose HP);

balancing, and after sample loading is finished, flushing 3-5 column volumes with A solution;

eluting with 0-25% B solution, wherein the elution volume is 20 column volumes, and collecting samples.

Comparative example 1: method for detecting PEG (polyethylene glycol) combination number of PEG (polyethylene glycol) site-directed modified asparaginase by fluorescence amine method

The experimental steps are as follows:

1 preparation of related solutions

Preparation of 1.10.3% fluorescamine acetone solution

6mg of fluorescamine was weighed out and dissolved in 20mL of acetone, and stored in the dark.

1.2 reaction buffer

5.3mL of 0.2mol/L sodium dihydrogen phosphate solution and 94.7mL of 0.2mol/L disodium hydrogen phosphate are taken, the volume is adjusted to 1L by water, the pH value is adjusted to 8.0, and the mixture is filtered for later use.

2 BCA method for determining protein content

2.1 preparation of working fluid

According to the number of the standard and the sample, 50 volumes of the BCA reagent and 1 volume of the Cu reagent (50:1) are prepared into a BCA working solution, and the BCA working solution is fully mixed (turbidity may occur during mixing, but the BCA working solution disappears after mixing). The BCA working solution is stable within 24 hours at room temperature.

2.2 dilution of standards

mu.L of the BCA standard was diluted to 100. mu.L with PBS (samples can be diluted with PBS in general) to a final concentration of 0.5 mg/mL.

2.3 BCA assay

The standard was added to the protein standard wells of a 96-well plate in an amount of 0. mu.L, 2. mu.L, 4. mu.L, 6. mu.L, 8. mu.L, 12. mu.L, 16. mu.L, 20. mu.L, and PBS was added in an amount of 20. mu.L, 18. mu.L, 16. mu.L, 14. mu.L, 12. mu.L, 8. mu.L, 4. mu.L, 0. mu.L. The sample is diluted appropriately (preferably in several gradients, 2-fold, 4-fold, 8-fold dilutions) and 20. mu.L is added to the sample wells of a 96-well plate. Because of pipette error in taking small amounts, the point in front of the standard line may not be very accurate, so the sample point is allowed to fall as far as possible behind the standard line 1/2. 200 μ LBCA medium was added to each well and left at 37 ℃ for 20 minutes. A562nm was measured by a microplate reader, and the protein concentration was calculated from the standard curve. When using incubator to incubate, should pay attention to prevent to influence the testing result because of moisture evaporation.

2.4 calculating the protein concentration in the test solution from the linear regression equation and multiplying by the dilution factor to obtain the final product

3 amino modification degree measurement

3.1 preparation of unmodified protein Standard stock solution

According to the protein concentration measured by the BCA method, the unmodified protein was diluted to 100. mu.g/mL with the reaction buffer as an unmodified protein standard stock solution.

3.2 preparation of modified protein Standard stock solution

According to the protein concentration measured by the BCA method, the modified protein is diluted to 100. mu.g/mL by using the reaction buffer solution, and the modified protein is used as a modified protein standard stock solution.

3.3 unmodified protein Standard Curve assay

Transferring 20 mul, 40 mul, 60 mul, 80 mul, 100 mul and 120 mul to 4mL of unmodified protein standard stock solution (100 mug/mL), and respectively diluting to 1.5mL by using phosphate buffer solution to obtain unmodified protein standard gradient solution; respectively adding 0.5ml of 0.3% fluorescamine acetone solution, violently shaking and mixing on a shaking mixer, standing at room temperature for 8 minutes, and measuring the fluorescence value (the excitation wavelength is 380nm, and the emission wavelength is 475nm) to obtain a standard curve of the fluorescence value and the protein concentration.

3.4 Standard Curve determination of test sample

Modified protein standard stock solutions (100. mu.g/mL) were removed in 20. mu.l, 40. mu.l, 60. mu.l, 80. mu.l, 100. mu.l, 120. mu.l to 4mL centrifuge tubes and assayed as in 3.3.

3.5 calculation formula

PEG binding number ═ 1- (slope of standard curve of test solution/slope of standard curve of unmodified protein) ] × number of modified sites

The results of the detection of the number of PEG-conjugated molecules are shown in the following Table 1:

TABLE 1

The results show that there is no obvious corresponding relationship between the amount of PEG binding and the detection result, and the detected PEG binding number is far higher than the actual PEG binding number. The reason is that the PEG modifier (Y-PALD-40K) has larger steric hindrance and can block the exposure of free amino sites, so that the detection result of PEG is higher by the fluorescence amine method.

Comparative example 2: the PEG binding number of PEG site-directed modified asparaginase is detected by adopting the principle of 3202 polyethylene glycol residual quantity measuring method of the fourth rule of Chinese pharmacopoeia

The method calculates the PEG combination number by detecting the total PEG content in a sample.

The experimental steps are as follows:

1. solution preparation:

barium chloride solution: weighing 5g of barium chloride, adding water to dissolve the barium chloride to l00mL, and uniformly mixing to obtain the barium chloride.

lmol/L iodine solution: weighing 2.0g of potassium iodide, adding a small amount of water for dissolving, then adding 1.3g of iodine, adding water to 50mL, and shaking up to obtain the potassium iodide.

YPALD-40K solution: accurately weighing 5mg YPALD-40K powder, adding water to dissolve to 50mL, making into solution containing 100 μ g polyethylene glycol per 1mL, mixing well, and standing.

2. The specific process comprises the following steps:

taking a proper amount of a test sample, and diluting with water to ensure that the protein concentration is not higher than 1 percent, thus obtaining the test sample solution. Precisely measuring 1.0mL of a test solution, adding 5.0mL of 0.5mol/L high chloric acid solution, uniformly mixing, standing at room temperature for 15 minutes, and centrifuging at 4000 rpm for 10 minutes. Taking 4mL of supernatant, adding l.0mL of barium chloride solution and 0.5mL of 0.lmol/L iodine solution, uniformly mixing, reacting for 15 minutes at room temperature, and measuring absorbance at 535nm of wavelength; meanwhile, lmL water is used to replace the test solution, and the same operation is carried out, thus obtaining the blank control.

3. Preparation of a standard curve:

and (3) taking the polyethylene glycol reference substance stock solution, diluting the polyethylene glycol reference substance stock solution with water to prepare 1.0mL of polyethylene glycol reference substance solution containing 10, 20, 30, 40 and 50 mu g of the polyethylene glycol reference substance per lmL, adding 5.0mL of 0.5mol/L high chloric acid solution, uniformly mixing, and carrying out the same operation from 'standing at room temperature for 15 minutes'.

4. And (3) calculating:

and performing linear regression on the corresponding absorbance by using the concentration (mu g/mL) of the polyethylene glycol reference solution, and substituting the absorbance of the test solution into a linear regression equation to calculate the content (mu g/mL) of polyethylene glycol in the test solution.

The results of the detection of the number of PEG-conjugated molecules are shown in Table 2:

TABLE 2

Number of PEG bonded	ASP+PEG	PEG-ASP double repair	Sample after enzymolysis	PEG-ASP double repair + PEG
					For the first time	1.70	0.84	0.72	3.2
For the second time	2.80	2.13	2.03	3.98

(remark: ASP + PEG: sample solution prepared by mixing ASP and PEG (Y-PALD-40K) in a molar ratio of 1: 2; sample after enzymolysis: treated PEG-ASP double-modified sample prepared by the same method as in example 1, procedure 1, sample solution preparation; PEG-ASP double-modified + PEG: sample solution prepared by mixing PEG-ASP double-modified sample and PEG (Y-PALD-40K) in a molar ratio of 1: 2.)

From the above results, it is clear that the parallelism of the results of 2 times is not good, and the actual detection result is greatly different from the theoretical value. The method is only suitable for measuring the residual value of trace polyethylene glycol, and has more limited factors if being used for measuring the total amount of PEG enzymolyzed from protein.

Comparative example 3 detection of PEG-binding number of PEG-site-directed modification of asparaginase by ammonium Cyhalothioate-chloroform two-phase System method

The method has the action principle that the amphoteric effect of PEG is utilized, ammonium iron thiocyanate solvated by the PEG is distributed in two phases and enters a chloroform layer phase, and the absorbance value is in direct proportion to the amount of the PEG under the wavelength of 510nm, so that the content of the PEG is directly analyzed and detected, and the PEG binding number is directly calculated.

The specific steps for detecting the PEG binding number of the PEG site-specific modified asparaginase are as follows:

1. pretreatment of the sample: 100 mu L of PEG site-directed modified asparaginase solution with known protein content is taken and placed for 15min at 100 ℃, 4 mu L of pancreatin (purchased from amresco, the product number: 0458-250G) is added, and enzymolysis is carried out for 20h at 37 ℃ for later use.

2. Ammonium iron thiocyanate solution: weighing 7.2g of ferric trichloride hexahydrate and 6.88g of ammonium thiocyanate, and adding water to a constant volume of 200mL for later use.

3. Y-PALD-40K PEG solution: accurately weighing 10mg of Y-PALD-40K PEG powder, adding water to constant volume, dissolving to 4mL to obtain solution containing 2.5mg of polyethylene glycol per lmL, mixing well, and standing.

4. Taking 1mL of prepared ammonium iron thiocyanate solution and 1mL of chloroform solution to form a two-phase system solution.

5. Preparation of a standard curve: respectively taking 5 mu L, 10 mu L, 20 mu L, 40 mu L, 60 mu L, 80 mu L and 100 mu L of accurately prepared aqueous solution of Y-PALD-40K PEG solution (2.5mg/mL), adding the aqueous solution into an ammonium ferrocyanide-chloroform two-phase system, oscillating for 2-3 h at 30-37 ℃, centrifuging for 2min, and determining the absorbance value of the chloroform phase solution at the wavelength of 510 nm.

6. Measuring the absorbance value of the sample: adding the pretreated sample solution into an ammonium iron thiocyanate-chloroform two-phase system, oscillating for 2-3 h at 30-37 ℃, centrifuging for 2min, and measuring the absorbance value of the chloroform phase solution at the wavelength of 510 nm.

7. Linearly regressing the corresponding absorbance by the concentration (mug) of the polyethylene glycol reference solution, substituting the absorbance of the test solution into a linear regression equation to calculate the content (mug) of the polyethylene glycol in the test solution, and calculating the binding number of the polyethylene glycol.

The method needs to search the temperature, time and the like in the

steps

5 and 6, and the temperature and time after oscillation at 30-37 ℃ for 2-3 h are the most appropriate temperature and time established through a large number of experiments. In the case of no temperature control, the change in absorbance values is shown in Table 3, and the PEG content and absorbance values do not have a clear linear relationship.

TABLE 3

PEG(μg)	12.5	25	50	100	150	200	250
								Absorbance value	0.093	0.078	0.111	0.106	0.065	0.116	0.064

Although a lot of experiments establish that the proper condition of 'oscillation at 37 ℃ for 3 h' has a remarkable linear relation between the PEG content and the absorbance value (see table 4 and figure 1), the PEG-ASP double-modified samples of 20151101S, 20151102S and 20151201S in three different batches have larger value fluctuation and poorer repeatability and accuracy when the PEG binding number is detected for multiple times at different time (see table 5).

TABLE 4

PEG(μg)	Blank space	12.5	25	50	100	150	200	250
									Absorbance value	0.132	0.113	0.159	0.182	0.394	0.507	0.64	0.749
Difference value	--	-0.019	0.027	0.05	0.262	0.375	0.508	0.617

TABLE 5

Example 1 PEG Release + SDS-PAGE electrophoresis method for detecting PEG site-directed modification of asparaginase PEG binding number

1. Procedure of operation

The complete operation process of detecting the PEG binding number of the PEG modified protein by a PEG release + SDS-PAGE electrophoresis method is illustrated by taking sample treatment by enzymolysis, iodine staining after SDS-PAGE electrophoresis and quantification by Quantity One software as an example:

preparation of pancreatin solution: accurately weighing 2.5g of pancreatin powder, adding 100mL of PBS for dissolving, uniformly mixing to avoid foam and protein damage, filtering and sterilizing, and standing at 4 ℃.

Preparation of sample solution: taking 500 μ L of test solution with known protein content, standing at high temperature for 15min, adding 40 μ L of pancreatin solution, and performing enzymolysis in water bath at 37 deg.C for 20 h.

Preparing Tris-HCl buffer solution with pH8.8: 9.08g Tris was dissolved in 40mL purified water, adjusted to pH8.8 with 4mol/L hydrochloric acid, added to 50mL purified water and stored at 4 ℃.

Preparing Tris-HCl buffer solution with the pH value of 6.8: 6.06g Tris was dissolved in 40mL purified water, adjusted to pH6.8 with 4mol/L hydrochloric acid, added to 50mL purified water and stored at 4 ℃.

Sodium dodecyl sulfate 10% (SDS): 10g SDS, dissolved in purified water and made to volume of 100mL, and stored at room temperature.

5 × Tris-glycine electrophoresis buffer: 15.1g of Tris and 94g of glycine (electrophoresis grade) (pH8.0) were dissolved in 900mL of purified water, and then 50mL of 10% SDS (electrophoresis grade) or 5g of SDS was added to make up to 1000mL of purified water.

5 × non-reducing loading buffer: measuring 1.25mL of 1M Tris-HCl (measuring 1M Tris, measuring 200mL of double distilled water for dissolution, and adjusting the pH value to 6.8 by HCl for later use); weighing 25mg of BPB and 2.5mL of glycerol, and placing the mixture in a 10mL plastic centrifuge tube; adding deionized water to dissolve, and fixing the volume to 5 mL; and subpackaging 500 mu L of the solution with constant volume and storing at room temperature.

The ratio of SDS-PAGE gels was prepared as follows:

preparation of 12% SDS-PAGE separation gel: h₂O (1.6mL), 30% acrylamide (2.0mL), 1.5M Tris-HCl (pH8.0) (1.3mL), 10% SDS (0.05mL), 10% ammonium persulfate (0.05mL) TEMED (0.002mL)

Preparation of 12% SDS-PAGE concentrated gel:

H₂o (1.4mL), 30% acrylamide (0.33mL), 1.5M Tris-HCl (pH6.8) (0.25mL), 10% SDS (0.2mL), 10% ammonium persulfate (0.2mL) TEMED (0.002mL)

Preparing 5mL of separation glue required by each rubber plate, adding the separation glue into a rubber plate mold, adding isopropanol to fill the container, pressing the separation glue to be flat, and standing for about 30-60 minutes (the separation glue needs to be solidified due to different room temperatures and different polymerization times); then, pouring off the isopropanol on the upper layer, adding 2mL of concentrated glue into each rubber plate, immediately inserting the comb teeth after the rubber plates are fully added, and standing for a period of time (the concentrated glue is required to be solidified due to different room temperatures and different polymerization times) for use.

Preparing a Y-PALD-40K PEG solution: accurately weighing 10mg of Y-PALD-40K powder, adding water to dissolve to 4mL, making into solution containing 2.5mg of Y-PALC-40K PEG per lmL, mixing well, and standing.

Preparation of standard gradient solution: adding 5 μ L, 10 μ L, 20 μ L, 30 μ L, 40 μ L and 50 μ L of Y-PALD-40K PEG solution (2.5mg/mL) into purified water to obtain gradient solution with final volume of 100 μ L, and mixing to obtain standard gradient solution.

Preparation and loading of samples: and respectively taking 100 mu L of the standard gradient solution and the test solution, adding 25 mu L of 5 Xnon-reduced sample loading buffer solution, mixing uniformly, and centrifuging, wherein the sample loading amount is 8 mu L. The sample application time is as short as possible, and sample diffusion and edge effects are avoided.

And (3) electrophoresis process: sequentially loading samples according to the sequence, covering a cover of the vertical electrophoresis apparatus after sample adding is finished, linking a power supply of the electrophoresis apparatus, turning on a power switch of the electrophoresis apparatus, and adjusting the initial voltage to 80V for about 30-40 min; when the separation gel enters, the voltage is adjusted to 120V-150V, and the time is about 1.5-2.0 h; when the bromophenol blue migrates to the bottom of the gel, stopping sample running, taking out the albumin gel, and performing iodine staining for color development according to the following method:

preparation of 10% perchloric acid solution: 100mL of perchloric acid is measured by a measuring cylinder and slowly added into 900mL of water, and the mixture is uniformly mixed to obtain the perchloric acid.

Preparing an iodine dye solution: accurately weighing BaCl₂17.5g of powder, 6g of KI powder and I₂The powder 3.9g was dissolved in 500mL of double distilled water and stored in the dark.

Iodine dyeing: after electrophoresis is finished, prying the glass plate, marking the film, placing the film in a dyeing box, fixing the film for 10min by using a 10% perchloric acid solution, washing the film for 3 times by using water, then covering the film with an iodine dye solution for dyeing, developing the color within about 1min, and immediately decoloring the film for 3-4 times by using water to take a picture.

Data processing: and (4) exporting the photos to a camera, and performing quantitative function processing by using Quantity One 4.4.0 software.

Some of the parameters: for example, the adjustment of electrophoresis voltage and current, the preparation of standard gradient solution, the adjustment of sample loading amount and the like in a certain range have no obvious influence on the experimental result. The enzymolysis conditions are the above pancreatin with the highest enzymolysis efficiency at the pH value of 7.5-8.5 and the temperature of 37 ℃, and the optimal enzymolysis conditions of the specific enzymes are the common knowledge of the technicians in the field. In addition, the components, the content, the preparation method and the like of the gel adopted by SDS-PAG E electrophoresis are conventional technical means, and the components, the content and the like of the gel can be determined according to the molecular weight of a sample to be detected.

2. And (3) detection results:

2.1 three different batches of PEG-ASP double-modified samples were tested according to the method "1, procedure" and the results are shown in Table 2 below:

serial numbers 1-6Std1-6 are standard gradient solutions, 7-9U1-U3 are PEG-ASP double-modification sample solutions of three different batches respectively, and serial number 10B1 is blank. Calculating the PEG binding number according to the above results, and the calculation formula is as follows:

(remark: PEG mol number: PEG mass/PEG molecular weight (40KD), protein mol number: protein concentration × sample volume (0.1 mL)/protein molecule (136KD), substituting the above data into the calculation to obtain the coefficient 34)

TABLE 6

The results show that the PEG binding number measured by the method of the invention is in accordance with the theoretical value, and the batch precision is better.

2.2 the PEG binding number of the PEG-ASP double-modified samples of 20150902S batches with different loading amounts is detected according to the method of '1, operation process', and the results are as follows:

TABLE 7

Calculating the combination number according to the results:

TABLE 8

(Note: 20150902S concentration is 1.8mg/mL)

The results show that the adjustment of the loading amount has no influence on the experimental results.

2.3: to verify the repeatability and accuracy of the method, the PEG binding number of the PEG-ASP double-modified sample of 20150902S batch was determined according to the method "1, procedure" and the determination was repeated 4 times, with the results as follows:

TABLE 9

Watch 10

The results show that the repeatability and the accuracy of the method for detecting the PEG binding number of the PEG modified protein medicine are good.

Example 2 PEG Release + SDS-PAGE electrophoresis method for detecting average PEG binding number of PEG randomly modified asparaginase

The detection method refers to example 1 "1, operation process", but the enzymolysis time is properly prolonged, and the hydrolysis is carried out in water bath for at least 48h, so as to ensure that the PEG in the sample must be completely released, and the detection results of the PEG binding number are shown in the following tables 3, 11 and 12:

(remark: PEG mol number: PEG mass/PEG molecular weight (5KD), protein mol number: protein concentration × sample volume (0.1 mL)/protein molecule (136KD), and the coefficient is obtained by substituting the above data into calculation 272)

TABLE 11

TABLE 12

The theoretical value of PEG (polyethylene glycol) binding number of PEG randomly modified asparaginase is 17-25, and the results prove that the PEG binding number of the PEG randomly modified asparaginase can be detected by using the method. And also that the methods of the present invention are not limited to a particular type of PEG modifier.

Example 3PEG Release + SDS-PAGE electrophoresis to detect PEG-ADI PEG conjugation

Preparation of standard solution: preparing a Novel-2-arm-40K PEG solution: precisely weighing 10mg of Novel-2-arm-40K powder, adding water to the powder to dissolve the powder to 4mL, preparing lmL solutions containing 2.5mg of Novel-2-arm-40KPEG, namely polyethylene glycol stock solutions, uniformly mixing and standing.

Preparation of standard gradient solution: adding 2 mu L, 4 mu L, 6 mu L, 8 mu L, 10 mu L and 15 mu L of Novel-2-arm-40KP EG standard solution (2.5mg/mL) into purified water to prepare a gradient solution with the final volume of 100 mu L, and uniformly mixing to obtain the standard gradient solution.

In addition to the above steps, the other parameters of the steps refer to example 1 "1, procedure":

the results of the detection of the number of PEG-conjugated molecules are shown in fig. 4, table 13, and table 14:

watch 13

Calculating the PEG binding number according to the above results, and the calculation formula is as follows:

(remark: PEG mol number ═ PEG mass/PEG molecular weight (40KD), protein mol number ═ protein concentration × sample volume (0.1 mL)/protein molecule (96KD), substituting the above data into the calculation to obtain the coefficient 24)

TABLE 14

The results show that the PEG-modified ADI sample PEG binding number can be detected by using the method of the invention, and the method is not limited to the proprotein such as asparaginase and the specific type of PEG modifier.

Claims

The method for detecting the PEG binding number in the PEG modified protein comprises the following specific steps:

preparation of a test solution: taking a certain amount of test solution with known PEG modified protein content, performing high-temperature treatment, adding pancreatin solution, and performing enzymolysis in water bath for later use;

preparation of PEG standard gradient solution: accurately weighing PEG powder same as the sample to be detected, adding water for dissolving to prepare PEG standard solution with a predetermined content, mixing uniformly, standing, adding PEG standard solutions with different volumes at certain intervals into purified water to prepare gradient concentration solutions with the same final volume, and mixing uniformly to obtain standard gradient solutions;

preparation and loading of samples: taking the standard substance gradient solution and the sample solution respectively, performing SDS-PAGE electrophoresis experiment, and taking a picture after color development by an iodine staining method;

data determination and calculation: quantitatively measuring and calculating the gray value of each dyed lane by using Quantity One 4.4.0 software on the photo; drawing a standard curve of the concentration and the gray value of the PEG standard substance according to the corresponding concentration of the gray value of the staining lane of the PEG standard substance gradient solution; substituting the gray value of the corresponding dyed lane of the test solution into the standard curve, and calculating to obtain the content of all free PEG in the test solution;

calculation of the number of PEG-conjugates: calculating the PEG binding number according to the above results, and the calculation formula is as follows:

PEG binding number = PEG moles protein number = PEG mass ÷ PEG molecular weight ÷ protein mass × protein molecular weight.