Search

Self-interaction of macromolecules has been shown to play an important role in a number of physical processes, including crystallization, solubility, viscosity, and aggregation. Peptide self-interaction is not as well studied as for larger proteins, but should play an equally important role. The osmotic second virial coefficient, B, can be used to quantify peptide and protein self-interaction. B values are typically measured using static light scattering (SLS). Peptides, however, do not scatter enough light to allow such measurements. This study describes the first use of self-interaction chromatography (SIC) for the measurement of peptide B values because SIC does not have the molecular size limitations of SLS. In the present work, SIC was used to measure B for enfuvirtide, a 36-amino acid therapeutic peptide, as a function of salt concentration, salt type, and pH. B was found to correlate strongly with solubility and apparent molecular weight. In general, the solubility of enfuvirtide increases with pH from 6 to 10 and decreases as the salt concentration increases from 0 to 0.5M for three different salts. The effect of peptide concentration on B was also investigated and shown to have a significant effect, but only at high concentrations (>80 mg/mL).

A method is described to enhance the resolution and detection sensitivity of proteins, peptides, and amino acids in capillary electrophoretic analysis of solution mixtures. The method consists of derivatizing the analytes with fluorescamine, which is normally used as a fluorogenic reagent for compounds containing a reactive primary amine functional group, and then using the derivative as an ultraviolet chromophore to enhance detection sensitivity (measured at 280 nm) in capillary electrophoresis. The results demonstrated a significant improvement in the separation and detection sensitivity of the derivatized analytes as compared to their underivatized counterparts. The use of chromophores, such as fluorescamine, in capillary electrophoresis facilitates the analysis of components of solution mixtures, such as pharmaceutical formulations, that could not be resolved and/or detected by conventional capillary electrophoresis procedures.

A quantitative spectrophotometrc assay for the determination of proline and hydroxyproline is described. The assay is based on the derivatization of the imino acids with the fluorogenic chromophore fluorescamine and the separation of the derivatized analytes by capillary electrophoresis. Fluorescamine reacts efficiently with secondary amino acids to form nonfluorescent aminoenone type chromophores which are easily detected at the low UV region. The assay is simple, rapid, and offers a significant improvement in detection sensitivity when compared with standard colorimotric methods for determining these imino acids. Derivatization with fluorescamine also enhances the degree of resolution of the two imino acids, enabling baseline separation of the derivatized analytes.

Several methods are available for determining the components present in a typical pharmaceutical dosage form. Although some of these methods are simple and have received wide pharmaceutical industry acceptance over many years, several limitations still need to be overcome. Capillary electrophoresis was examined as an alternative method for the determination of a recombinant cytokine in a pharmaceutical dosage form. The results show that capillary electrophoresis can separate the recombinant cytokine from its dosage form matrix adequately, rapidly and with minimum sample volume requirements. Owing to its high efficiency, high resolution and simplicity, capillary electrophoresis appears to be very applicable to pharmaceutical samples. For reliable quantification of the resulting data, however, it is essential to optimize the experimental conditions, such as separation buffer and capillary column temperature. The advantages and potential of capillary electrophoresis for the separation of active ingredients and excipients in pharmaceutical formulations are discussed.

Due to the fact that some proteins have a tendency to bind to glass surfaces, plastic CZ-resin vials were evaluated as an alternative material to glass vials for packaging protein-based parenteral formulations. Physico-chemical tests including protein binding, extractable evaluation, oxygen permeation, light transmission and moisture loss were performed. Data show that two proteins (A and B) were found to bind to USP type I glass but not to CZ-resin. The CZ-resin vials passed all USP test specifications for extractables (organic extractable, non-volatile residue and residue on ignition). The oxygen permeation rate (79.06 cm(3)mm/m(2)24 h atm) was consistent with that reported by the vendor (67 cm(3)mm/m(2)24 h atm). The value obtained for light transmission, which was also found to be consistent with that reported by the vendor, shows that these vials offer no protection from light. The average moisture loss from 2 cm(3) vials filled with water was gravimetrically determined to be 0.04 mg/day/vial when the vials were stored at 40 degrees C/75% relative humidity (RH). Assuming a 1cm(3) product fill, this corresponds to approximately a 3% loss over a 2-year period. However, moisture loss was found to be negligible at the typical storage condition of 5 degrees C for protein formulations. The physico-chemical tests indicate that CZ-resin vial is a suitable candidate for packaging parenteral formulations since it shows low moisture loss at typical storage condition of 5 degrees C, and does not leach out extractables. However, it should not be used for light-sensitive and oxygen-sensitive parenteral formulations. For proteins A and B, the CZ-resin vial is a viable alternate to the use of glass vials since it offered significantly less protein binding. Protein binding in general, should be evaluated on a case by case basis, since it may vary for different proteins and under different formulation conditions.

Capillary electrophoresis has proved to be a versatile method for the determination of proteins, peptides and amino acids in pharmaceutical formulations. For quantification of the capillary electrophoresis data, however, significant errors may result if the analysis is performed using improper separation conditions. The peak area response for protein analytes, which is generally low in conventional UV detection, may also vary dramatically depending on the nature of the buffer used in the separation. This paper describes the effects of various buffer constituents and analytical conditions on the capillary electrophoretic separation and quantification of a humanized monoclonal antibody in bulk form and in a typical therapeutic formulation. For optimum peak area response and reproducibility, protein derivatization with an appropriate chromophore (e.g., fluorescamine) and separation in the presence of a moderate ionic strength buffer containing lithium chloride, tetramethylammonium chloride or trimethylammonium propylsulfonate is recommended. General guidelines for the determination of proteins by capillary electrophoresis and a rationale for the use of internal standards to improve the quantification of data are also discussed.

A purified glycoprotein, designated RSL-major, was isolated from the rat sublingual gland by means of the procedure of Tettamanti and Pigman. It was found to be homogeneous by analytical ultracentrifugation, to have a mol. wt. of 2-2 times 10-6, and to contain 81 percent (W/W) of carbohydrate, which consists mainly of sialic acid, 2-acetamido-2-deocy-D-glucose, 2-acetamido-2-deocy-D-galactose, and D-galactose in the molar ratio of 1.4:1.4:1.0:1.5; small amounts of fucose and mannose [1.2 and 2.8 percent (W/W), respectively] were also present. The sialic acid residues were resistant to the action of V. cholerae neuraminidase. This resistance was completely abolished by removal of the O-acetyl groups contained in the sialic acid. The sialic acid in RSL-major appeared to be a mixture of N-acetyl-4-O-acetyl- and N-acetyl-4, 7(8)-di-O-acetylneuraminic acids. The carbohydrate to protein attachment of RSL-major was shown, by alkaline beta-elimination reaction, to consist of an O-glycosyl linkage between 2-acetamido-2-deoxy-D-galactosyl residues in the oligosaccharide chains and seryl and threonyl residues in the protein core. The average oligosaccharide, contained in RSL-major, was postulated to be a heptasaccharide. A second material, designated RSL-minor, and also isolated from the ratsublingual gland, was obtained as a mixture of glycoprotein(s) and hydroxylapatite gel, and was not purified further.

It has been shown that dimethylsulfoxide is useful in separating protein contaminants and minor mucins from the submaxillary glycoproteins prepared by the method of Tettamanti, G. and Pigman, W. (1968) Arch. Biochem. Biophys., 124, 41–50. In addition, alkaline dimethylsulfoxide was found to greatly accelerate the β-elimination reaction of glycoproteins. As this procedure does not produce diffusible protein fragments, it should be of value in studies of the protein core and for the investigation of those protein-carbohydrate linkages that are resistant to treatment by alkali. Optimal conditions for carrying out the β-elimination and reduction reactions of bovine submaxillary glycoprotein in aqueous alkaline NaBH4 systems have been described. Under such conditions, the conversion of 2-aminopropenoic and 2-amino-2-butenoic acid residues into alanine and α-aminobutyric acid, respectively, is complete. This reduction procedure is of a broad application and can be used for the reduction of the phenylhydrazone derivatives of α-keto acids to the corresponding amino acids. A comparison of our procedure with that described by Simpson, L. D., Hranisavljevic, J. and Davidson, E. A. (1972) Biochemistry, 11, 1849–1856, shows that the method outlined here is superior both in efficiency and for quantitative recovery of unsaturated hydroxyamino acids.