Dichroism of bacteriochlorophyll in cells of the photosynthetic bacterium Rhodopseudomonas palustris

1. The dichroism was measured at varied wavelengths of polarized light in “intact” cells of Rhodopseudomonas palustris and in films of air-dried lamellar fragments of the bacterium.     

Chain conformation of copoly(γ-methyl D,L-glutamate)

Copolymers of γ-methyl D - and L -glutamates with various D /L ratios were prepared. Infrared absorption spectra of solid films were measured and sums of right- and left-handed helix contents were determined from intensities of amide V bands. Farultraviolet absorption spectra and optical rotatory dispersion of these copolymers in solutions are used to ascertain their helical character. Chain conformations of DL -copolypeptides are discussed.     

Fine structure of the epithelial reticular cells of the medulla of the thymus in the golden hamster

Summary The epithelial reticular cells of the thymic medulla of the golden hamster were studied by electron microscopy. On the basis of their structural details two cell types are distinguished, although the two types are similar in basic structure. The cells of one type are more extended in shape and darker in appearance. They are connected with one another by their cytoplasmic processes, forming a reticulum in the medulla. Thus they appear to play a supporting role as do the cortical epithelial reticular cells. The other cell type is larger, more rounded and lighter. The characteristic feature of this cell type is an abundance of vesicular structures, which occur as vesicles or vacuoles of varying sizes. In addition, an enormous, intracytoplasmic ciliated cyst is occasionally encountered in the latter cell type. The cyst may be regarded as representing a specialized form of the vesicular structures. The possible functional significance of the latter cell type is discussed in relation to recent concepts concerning the mechanism of thymic function.Dedicated to Professor W. Bargmann, under whose guidance my thymus studies were begun, in honor of his 60th birthday (T. Ito).     

Step-wise thermal denaturation of cobrotoxin,a snake venom neurotoxin fromNaja naja atra: A proton nuclear magnetic resonance study

Temperature dependence of proton nuclear magnetic resonance spectra has been followed for cobrotoxin, a postsynaptic neurotoxin fromNaja naja atra venom. Several aromatic amino-acid residues, including the functionally essential Trp-29 located at the tip of the central loop of the molecule, have been found to undergo a thermal structural transition above the global thermal denaturation temperature. It is suggested that a local structure around these residues behaves somehow independently of the rest of the molecule, and that such structural organization may be favorable for a conformational change of a neurotoxin molecule on binding to acetylcholine receptor.     

Similarity of the outer capsid protein VP4 of the Gottfried strain of porcine rotavirus to that of asymptomatic human rotavirus strains.

Genomic segment 4 of the porcine Gottfried strain (serotype 4) of porcine rotavirus, which encodes the outer capsid protein VP4, was sequences, and its deduced amino acid sequence was analyzed. Amino acid homology of the porcine rotavirus VP4 to the corresponding protein of asymptomatic or symptomatic human rotaviruses representing serotypes 1 to 4 ranged from 87.1 to 88.1% for asymptomatic strains and from 77.5 to 77.8% for symptomatic strains. Amino acid homology of the Gottfried strain to simian rhesus rotavirus, simian SA11 virus, bovine Nebraska calf diarrhea virus, and porcine OSU strains ranged from 71.5 to 74.3%. Antigenic similarities of VP4 epitopes between the Gottfried strain and human rotaviruses were detected by a plaque reduction neutralization test with hyperimmune antisera produced against the Gottfried strain or a Gottfried (10 genes) x human DS-1 rotavirus (VP7 gene) reassortant which exhibited serotype 2 neutralization specificity. In addition, a panel of six anti-VP4 monoclonal antibodies capable of neutralizing human rotaviruses belonging to serotype 1, 3, or 4 was able to neutralize the Gottfried strain. These observations suggest that the VP4 outer capsid protein of the Gottfried rotavirus is more closely related to human rotaviruses than to animal rotaviruses.     

Purification and characterization of exudate gelatinases in the chronic-phase of carrageenin-induced inflammation in rats

Gelatinases have been purified from the exudate in the chronic-phase (day 7) of carrageenin-induced inflammation in rats. The day-7 exudate gelatinases gave two peaks on Sephadex G-150 gel filtration, the initial step of the purification. The molecular weights of the gelatinases corresponding to the two peaks were about 300 kDa (HMW fraction) and about 110 kDa (LMW fraction), respectively. The gelatinase in the HMW fraction has been purified to homogeneity; the purified gelatinase gave a single band corresponding to a molecular weight of 57 kDa on both SDS-polyacrylamide gel electrophoresis (PAGE) and SDS-gelatin PAGE. On the other hand, the gelatinase purified from the LMW fraction was found to consist of three species, with molecular weights of 66, 64, and 57 kDa, as judged on SDS-gelatin PAGE. Granulation tissue-derived fibroblasts in culture mainly produced the 64-kDa species, which was converted to a 57-kDa species on treatment with 4-amino-phenylmercuric acetate, while rat macrophages and polymorphonuclear leukocytes mainly secreted the 96-kDa species. These results suggest that exudate gelatinases are largely produced by fibroblasts in granulation tissue and that they bind to exudate proteins, resulting in the formation of complexes with molecular weights of about 300 kDa and about 110 kDa. The gelatinases purified from the HMW and LMW fractions are metalloproteinases, as judged from the results of inhibitor experiments. Both the gelatinases degraded gelatin, but showed to proteolytic activity toward alpha-casein or type I collagen. Type IV collagen was degraded at 35 degrees C by the gelatinases purified from the LMW fraction but not by that from the HMW fraction.