Using an improved method of gel electrophoresis, many hitherto unknown proteins have been found in bacteriophage T4 and some of these have been identified with specific gene products. Four major components of the head are cleaved during the process of assembly, apparently after the precursor proteins have assembled into some large intermediate structure.

Cleavage of Structural Proteins during the Assembly of the Head of Bacteriophage T4

Cleavage of structural proteins during the assemble of the head of bacterio-phage T4

The reliability of molecular weight determinations by dodecyl sulfate-polyacrylamide gel electrophoresis

Electrophoretic analysis of the major polypeptides of the human erythrocyte membrane.

https://www.jbc.org/content/252/3/1102.full.pdf

Peptide mapping by limited proteolysis in sodium dodecyl sulfate and analysis by gel electrophoresis.

Molecular weight estimation of polypeptide chains by electrophoresis in SDS-polyacrylamide gels

Molecular weight estimation of polypeptides by SDS-polyacrylamide gel electrophoresis: further data concerning resolving power and general considerations.

Although numerous reports show that the sensitivity of the S cone system is decreased in diabetic patients, few studies have been directed toward identifying the possible sites of the sensitivity loss. In this study, a psychophysical technique was used to test hypotheses about sites of S cone system sensitivity loss in a group of patients with early diabetic retinopathy. A model of the S cone system was assumed and the experimental conditions were chosen to distinguish between explanations for S cone sensitivity loss at the receptor level from explanations for loss at a post-receptoral level. Within the context of the model, the data were consistent with S cone system sensitivity loss occurring at a post-receptoral level. Invest Ophthalmol Vis Sci 33:2781-2790, 1992 Diabetes is known to affect the sensitivity of the short wavelength sensitive (S) cone system. There are reports of tritan-type defects using hue discrimination techniques and reports of reduced S cone pathway sensitivity using spectral sensitivity techniques. These defects are evident even in the early stages of diabetic retinopathy. 1 " 5 These measurements, however, reflect the sensitivity of the S cone system as a whole and thus do not provide sufficient information for identifying the anatomical sites or physiologic mechanisms of S cone sensitivity loss. The anatomic sites may be at the level of the inner retina, reflecting a disturbance of retinal circulation. Evidence for inner retinal dysfunction comes from reports of reductions in the scotopic threshold response amplitude 6 and in oscillatory potential amplitudes 7 " 9 in patients with mild degrees of retinopathy. It is possible, however, that inner retinal disease may compromise outer retinal function,

Psychophysical evidence for post-receptoral sensitivity loss in diabetics.

Methods for the separation and identification of the polypeptide chains of each lens crystaUin are basic to the study of these proteins on polyribosomes. Rabbit lens proteins have been deaggregated, denatured, and reduced to polypeptide chains, and separated by polyacrylamide gel electrophoresis. Approximate molecular weights of the resultant chains have been calculated by the same system. Vigorous denaturation and reduction with sodium dodecyl sulfate and 2-mercaptoethanol disrupts all structure other than primary structure, degrading each protein to its component polypeptides. The separation method employed is almost exclusively dependent on molecular size. Deaggregated alpha crystaUin is a group of chains, each of about 20,000 molecular weight. The beta crystaUin region of the DEAE chromatogram yields three polypeptides of estimated molecular weights 21,000, 23,000, and 29,000. Preliminary studies on the four beta crystaUin peaks isolated, by DEAE-chromatography suggest that one or more may be composed of aggregates of different polypeptide chains. Gamma crystallins appear to be single polypeptide chain proteins of molecular weights from 18,000 to 21,000. Experiments performed on lens epithelium indicate that a significant percentage of their newly synthesized proteins are nuclear and cytoplasmic proteins other than the crystallins.

Studies on Lens Protein Polypeptides

DEAE-purified rabbit beta crystallins have been studied by sedimentation on sucrose gradients ami their subunits characterized by co-electrophoresis in SDS-polyacrylamide gels. The experiments indicate that the beta crystallins isolated by DEAE-cellulose are a large family of related proteins with sedimentation velocities of about 4S. Deaggregation and denaturation of these proteins to polypeptides and subsequent electrophoretic analysis yields three groups of subunits with calculated, molecular weights of 21,000, 23,000, and 29,000. The minimum total number of polypeptide chains in the three groups is five. Each of the beta crystallins is made up of two or three such chains. Aggregation and loss of solubility occur readily during concentration procedures. In the course of these experiments, it became evident that alpha crystallin is composed of at least two different sizes of polypeptide chains.

Arnold L. Shapiro

Papers

Molecular weight estimation of polypeptide chains by electrophoresis in SDS-polyacrylamide gels

Molecular weight estimation of polypeptides by SDS-polyacrylamide gel electrophoresis: further data concerning resolving power and general considerations.

Psychophysical evidence for post-receptoral sensitivity loss in diabetics.

Studies on Lens Protein Polypeptides

Subunit Composition of Rabbit Lens Beta Crystallins