The band areas of proteins determined by fluorescent scanning in the commercial automated gel electrophoresis apparatus.

An automated gel electrophoresis apparatus, recently available commercially, allows one to follow the band during electrophoresis in real time, and lends itself therefore to an evaluation of bandwidth as a function of migration time (the dispersion coefficient), resolution and band shape. These determinations assume the constancy of band area with migration time and at various gel concentrations. The purpose of the present study was to verify these assumptions. Representative proteins and sodium dodecyl sulfate (SDS)-proteins, either natively fluorescent or fluorescein carboxylate labeled, were found to exhibit band areas which approach constancy as a function of migration time in both agarose and polyacrylamide gel electrophoresis, provided that (i) the protein concentration under the band was low enough to obviate self-quenching of fluorescence; (ii) the separation of the protein of interest from contaminants had progressed sufficiently during the time at which band areas were measured; (iii) the baseline under the peak was sufficiently well defined. However, band areas decrease with increasing gel concentration. Protein peaks exhibited leading and trailing tails. The ratio of the combined tail area to total area appeared to be near-constant at varying migration times. However, that ratio increases with increasing gel concentration. The tail area does not appear to be an artifact of fluorometric detection since it is reproduced upon fluorimetric analysis of the protein eluted from gel slices after electrophoresis. However, it may be due to photochemical destruction under the conditions of repetitive fluorometric peak detection.

The relative contributions of dispersion and diffusion to band spreading (resolution) in gel electrophoresis.

DNA of approximately 2 kbp in length was previously found not to diffuse significantly in 1-1.5% agarose gels in the absence of an electric field, but to disperse during electrophoresis (Yarmola, E., Chrambach, A., Electrophoresis 1995, 16, 345-349). Accordingly, a process distinct from diffusion, and responsible for band spreading with migration time in gel electrophoresis, was defined as dispersion. Correspondingly, the diffusion coefficient, D(diff), was distinguished from a dispersion coefficient, D(disp). For DNA of approximately 1, 2 and 3 kbp, D(diff) and D(disp) were measured in agarose gel electrophoresis (1.0% SeaKem GTG). In that order of DNA length, D(disp)/D(diff) was found to increase from 5 to 15 to 45, showing that with increasing DNA length, time-dependent band spreading, and thus resolution in gel electrophoresis, is governed predominantly by dispersion, not diffusion. It is assumed that the essential part of electrophoretic dispersion is due to entanglement of the DNA molecule in the gel. Indirect evidence for such an entanglement derives from the observation of peak asymmetry and its interpretation by the Giddings-Weiss model.

Interpretation of electrophoretic band shapes by a partition chromatographic model.

Measurements of the shape of electrophoretic bands of phycoerythrin and conalbumin have been made at regular intervals during migration in agarose gels. Analysis of the peak shapes suggests the existence of a significant degree of asymmetry. This is to be contrasted with the symmetry around the peak associated with the generally assumed Gaussian band. The degree of asymmetry of the bands decreased as a function of time and increased with agarose concentration. A similar experiment on DNA indicated constancy of the degree of asymmetry as a function of time. These results can be interpreted as, but do not prove the validity of, a nonlocal diffusion equation which generalizes a theory originally put forth by Giddings and Eyring (J. Am. Chem. Soc. 1955, 59, 416-420). The results may be significant in framing a measure of the resolvability of electrophoretic peaks.

Soft tissue digital procedures.

The purpose of this article is to discuss the common soft tissue procedures used to correct the reducible digital deformities. The reader should keep in mind that often these procedures are used in combination with osseous techniques for semi- or nonreducible digital deformities.

Analysis of carprofen dosage forms and drug substance by high-performance liquid chromatography.

A high-performance liquid chromatographic method for the analysis of carprofen in solid dosage forms and as the bulk drug substance was developed. The simple, accurate, reproducible, and stability-indicating method was shown to be applicable to drug substance and dosage form stability studies, as well as the quality control of carprofen dosage forms.

Simultaneous high-performance liquid chromatographic determination of chlordiazepoxide and amitriptyline hydrochloride in two-component tablet formulations.

A rapid, precise, and accurate high-performance liquid chromatographic procedure is presented for the stimultaneous determination of amitriptyline hydrochloride and chlordiazepoxide in two-component tablet formulations. The impurities and decomposition products of both components were separated, making the determination specific for amitriptyline hydrochloride and chlordiazepoxide. The method was used for the assay, content uniformity, and dissolution testing of dosage forms containing 5--30 mg of chlordiazepoxide and 12.5--75 mg of amitriptyline.