Two-dimensional NMR and structure determination of salmon calcitonin in methanol

The structure of the 32-residue peptide salmon calcitonin (sCT) in 90% MeOH-10% H2O has been investigated by two-dimensional NMR techniques and molecular modeling. Sequential assignments for nearly all of the 32 spin systems have been obtained, and results indicate that the heptaresidue loop formed by the disulfide bond between Cys-1 and Cys-7 is followed by an alpha-helical segment from Val-8 through Tyr-22. A region of conformational heterogeneity is observed for residues 20-25, resulting from the slow isomerism of the cis and trans forms of Pro-23. The C-terminal segment is found to exist in an extended conformation.     

Characterization of two gangliosides from human leukemic polymorphonuclear leukocytes.

Eight bands of gangliosides, from human polymorphonuclear leukocytes were demonstrated by thin-layer chromatography. Bands 4 and 5 were isolated and purified in sufficient amounts to allow their biochemical identification by thin-layer chromatography, gas chromatography and sequential action of glycosidases and neuraminidase. The major ganglioside was characterised as N-acetylneuraminylgalactosyl-beta-N-acetylglucosaminyl-beta-galactosyl-beta-glucosylceramide. A second ganglioside was tentatively identified as N-acetylneuraminyl-galactosyl-beta-N-acetylglucosaminyl-beta-(N-acetylneuraminyl)galactosyl-beta-glucosylceramide. Both gangliosides isolated were hydrolysed by neuraminidase. However, treatment of the intact cells with neuraminidase did not alter the ganglioside pattern.     

Frequency response characteristics of electroreceptors in weakly electric fish (Gymnotoidei) with a pulse discharge

Summary Three species of Gymnotid fish, two species ofHypopomus andRhamphichthys rostratus, each having pulse type electric organ discharges (EOD) of different durations were studied to learn if any correlation exists between the spectral composition of the species specific EOD pulse and the frequency response characteristics of that species' electroreceptors. The receptor population consisted of two major categories (examples in Fig. 3). One category, termed pulse marker receptors, responded to suprathreshold stimulus pulses with a single spike at a short (<2 ms) latency. These receptors were tuned to the higher frequency components of a species' EOD (Fig. 4A) and were always 5 to 10 dB less sensitive than any other electroreceptors within a given species. The second major receptor category, burst duration coders, responded to an electrical stimulus with a burst of spikes at a longer latency, burst length was a function of stimulus amplitude. This second category could be further divided into three sub-categories according to the receptors' frequency response characteristics. The most commonly seen subcategory, wide band receptors (Fig. 4B), responded best to stimuli having frequencies equal to the dominant frequency component of the species' EOD in the two species ofHypopomus studied. A second subcategory, narrow band receptors (Fig. 4 A), had frequency response characteristics similar to those of the pulse marker receptors; however, these had thresholds 10 dB lower than those of the pulse marker. The third subcategory of burst duration coders, low frequency receptors (Fig. 4 C, D), responded best to stimulus frequencies ranging from about 50 to 150 Hz. Mechanisms of coding stimulus amplitude and responses to prolonged sinusoidal electrical stimuli were also studied in the various receptor types.It is suggested that the differences in the major receptor types and the different frequency response characteristics of the electroreceptors within a given species allows the animals to identify and evaluate signals resulting from their own EOD, the EODs of conspecifics and electrical stimuli generated by other species of electric fish.Supported by NIH Grant #1 RO1 NS 12337-01     

Lipid-protein interactions at the erythrocyte membrane. Different influence of glucose and sorbose on membrane lipid transition

When observed over a temperature range, erythrocyte membrane lipids undergo a transition at 18–20 °C (Zimmer, G. and Shirmer, H. (1974) Biochim. Biophys. Acta 345, 314–320). This observation has prompted an investigation of the effects that substrate binding has on the transition of the red cell membrane. Glucose and sorbose were compared, since transport kinetics of these sugars still pose unresolved questions.In membranes, preloaded with glucose, the break at the transition temperature was intensified, while it was abolished or reversed in membranes preloaded with sorbose.These results were corroborated using different solubilization procedures (sonication, sodium dodecyl sulfate treatment) of the membranes, and also different techniques (viscosimetry, 90° light scattering, 1-anilino-naphthalene-8-sulfonate fluorescence).In extracted membrane lipids, viscosimetry indicated a break at transition temperature after preloading with either glucose or sorbose.Disc electrophoresis revealed a different binding pattern of the two sugars.It is suggested, that the amplification of the discontinuity in red cell membranes by glucose and the abolition or reversal of the break by sorbose are mediated by membrane protein- and/or membrane lipid-protein interaction.     

Cylindrical laminated bodies in nickel-subsulphide-induced rhabdomyosarcoma in rabbits.

The induction of rabbit rhabdomyosarcoma was obtained after intramuscular implantation of a large quantity of very pure nickel subsulphide, though until the present time the rabbit was considered refractory to Ni3S2 tumorigenesis. These tumors are similar to those induced in rats under the same conditions. Four different cell types were observed: small polygonal cells, small elongated cells, giant cells, and mature myofibers. Electron microscopy reveals a complete disorientation of myofibrils in mature myoblasts. Giant cells appear by pluripolar endomitosis and always contain myofibrillar structures, but M-lines and Z-lines are not present in these cells. Cylindrical laminated bodies were observed very often in all four cell types. They are formed of 4 nm fibrils arranged in crossed position in each lamella. Some of these paracrystalline structures were also observed in nuclei. The laminated bodies are considered to be abnormal formations of contractile proteins produced during tumoral myofibrillar differentiation.     

A novel beta-endorphin binding protein. Complement S protein (= vitronectin) exhibits specific non-opioid binding sites for beta-endorphin upon interaction with heparin or surfaces

Human beta-endorphin (1-31) (beta H-endorphin) was found to specifically interact with purified complement S protein from human plasma. As found by chemical cross-linking beta H-endorphin bound to both, the 65- and 75-kDa molecular mass forms of S protein. The interaction of S protein with heparin as well as the adsorption of S protein to surfaces led to an almost 10-fold increase of specific binding which was due to the exposure of further beta H-endorphin-binding sites. The interaction of beta H-endorphin with S protein bore characteristics of a ligand-receptor interaction, such as time dependence, reversibility, high affinity, saturability, and structural specificity and was mediated through the non-opioid COOH terminus of the beta H-endorphin molecule. beta H-Endorphin binding to S protein was observed at physiological pH or cation concentrations, indicating that the interaction may well occur in vivo. Our results provide conclusive evidence that interactions of S protein with very different effectors led to similar conformational changes which uniformly resulted in exposure of a highly specific beta H-endorphin binding domain on S protein. With S protein as major beta H-endorphin-binding protein in the periphery, the molecular basis of a widespread system of humoral target sites of the neuroendocrine effector appears to be established. In view of S protein involvement in processes of inflammation and wound repair and beta-endorphin effects on immunocompetent cells, the demonstrated S protein-beta H-endorphin interaction appears to be of considerable functional significance.