Stereochemistry of the porphyrin-protein bond of cytochrome c. Stereochemical comparison of Rhodospirillum rubrum, yeast, and horse heart porphyrins c.

Porphyrins c have been obtained from Rhodospirillum rubrum cytochrome c2, yeast cytochrome c, and horse heart cytochrome c and compared using proton magnetic resonance and circular dichroism. Identity of the spectra establishes that chemically and stereochemically the three porphyrins c are identical. Since the stereochemistry of the porphyrin alpha-thioether linkage is not affected in the conversion to porphyrin c, the stereochemistry at the porphyrin alpha-thioether bonds among the corresponding cytochromes c also must be the same. Differences between the proton magnetic resonance of R. rubrum cytochrome c2 and horse heart cytochrome c which were rationalized by invoking an opposite stereochemistry at these condensation sites (Smith, G. M., and Kamen, M. D. (1974), Proc. Natl. Acad. Sci. U.S.A. 71, 4303) must therefore be attributed to other factors.     

Penicillinase activity in three strains ofClostridium butyricum

Three strains ofClostridium butyricum exhibited elevated minimal inhibitory concentrations (MICs) to penicillin (64–1,024 g/ml), ampicillin (32–256 g/ml), carbenicillin (128–1,024 g/ml), and oxacillin (32–64 g/ml). Cephalosporin/cephamycin agents were more active than penicillin drugs. All isolates were found to possess a -lactamase. The -lactamases were primarily cell associated during the logarithmic phase of growth. Stationary-phase cells released most of the enzyme into the culture medium. Cephalothin supplementation of broth cultures with concentrations equivalent to one-eighth of the MIC significantly increased the quantity of -lactamase synthesized. The -lactamases produced by these three isolates exhibited greatest activity with penicillin followed by ampicillin>cephaloridine>carbenicillin and oxacillin. No enzymatic activity was observed using cephalothin, cephalexin, cefazolin, cefoxitin, or cephamandole substrates. The -lactamases were inhibited by clavulanic acid and para-chloromurcuribenzoate and not inhibited by cloxacillin. Each enzyme exhibited an isoelectric point of 4.2.     

Factors Affecting the Toxic Effect of Tin on Estuarine Microorganisms

Inorganic tin (SnCl₄·H₂O) is toxic to microbial populations obtained from estuarine sediments plated on nutrient medium solidified with either agar or purified agar. The use of gelatin as a gelling agent decreased the apparent toxicity of tin, and toxicity was markedly reduced in medium solidified with silica gel. There was no evidence that toxic agar-tin complexes were involved. Cd, Cu, Pb, Ni, and Zn exhibited similar toxicity patterns; therefore, toxicity levels determined in the laboratory should be extrapolated to the environment with caution. The addition of cysteine to the medium had no effect on tin toxicity. Serine or 3-hydroxyflavone enhanced toxicity, while humic acids or gelatin inhibited toxicity. Replacement of SO₄²⁻ with NO₃⁻ did not alter tin toxicity, but replacement of Cl⁻ with NO₃⁻ decreased tin toxicity. Thus, the toxic effect(s) of tin depend as much on the chemical speciation of the metal as on the total concentration of the metal in the medium.     

Interaction of the carboxamide of NADPH with Lactobacillus casei dihydrofolate reductase

Dihydrofolate reductase from Lactobacillus casei and its complexes with NADPH and methotrexate yield well-resolved Raman spectra. The 1685-cm^?1 Raman band assigned to the carboxamide of NADPH persists in the NADPH-enzyme binary complex but is absent from the NADPH-methotrexate-enzyme ternary complex. This is ascribed to stabilization of the polarized form of the carboxamide by H bonding to the NH and CO groups of Ala 6 and Ile 13 of the peptide backbone.     

A previously unrecognized Isidrogalvia (Liliaceae) from Bolivia

Isidrogalvia longiflora, a new combination based onAsagraea longiflora, is proposed. It is the first record ofIsidrogalvia from Bolivia.     

Weeds of Kentucky and Adjacent States. A field guide. By Patricia Dalton Haragan The University Press of Kentucky, Lexington, KY 40506-0336

In 1843 S. B. Buckley (1809–1884) traveled up the St. Johns River, Florida in search of plants, shells, and possibly other natural history objects. Buckley encountered many difficulties in interior Florida and his trip did not live up to his original expectations. It was unfortunate that the took years to distribute his plant specimens, since few botanists or naturalists had preceded him into that poorly explored region.     

“That land of flowers,swamps and alligators”: S. B. Buckley’s 1843 trip up the St. Johns River,Florida

In 1843 S. B. Buckley (1809–1884) traveled up the St. Johns River, Florida in search of plants, shells, and possibly other natural history objects. Buckley encountered many difficulties in interior Florida and his trip did not live up to his original expectations. It was unfortunate that the took years to distribute his plant specimens, since few botanists or naturalists had preceded him into that poorly explored region.     

Interactions of surfactin,a biosurfactant fromBacillus subtilis,with inorganic cations

Summary The properties of surfactin, a biosurfactant lipopeptide, were highly modified in the presence of inorganic cations. The micellization of surfactin was favoured by monovalent and, especially by divalent cations with a modification of the molecular area at the air-water interface. Haemolysis of erythrocytes by surfactin was enhanced by low concentrations of divalent cations with an increase of the binding of the lipopeptide to membrane. Inorganic ions induced conformational rearrangements probably due to ion-surfactin associations which modify the surface-active properties.     

Isolation and characterization of two individual glycoprotein components from human milk-fat-globule membranes.

Two individual glycoprotein components from human milk-fat-globule membranes (MFGM) has been purified by selectively extracting the membrane glycoproteins followed by lectin affinity chromatography and gel filtration on Sephadex G-200 in the presence of protein-disaggregating agents. The purified glycoprotein components, termed 'epithelial-membrane glycoprotein' (EMGP-155 and EMGP-39) have estimated molecular weights of 155 000 and 39 000 respectively, and yield a single band under reducing conditions on sodium dodecyl sulphate/polyacrylamide gel. EMGP-155 and EMGP-39 contain 21.0% and 7.0% carbohydrate by weight, with fucose (13.5%, 12.4%), mannose (3.7%, 6.2%), galactose (28.5%, 22.6%), N-acetylglucosamine (17.8%, 7.4%) and sialic acid (36.4%, 51.4%) of the carbohydrate moiety respectively. For both the glycoprotein components, aspartic and glutamic acid and serine are the major amino acid residues.