The terminal structures of feather keratin mRNA

Terminal labeling of embryonic feather keratin mRNA with [³H]KBH₄ followed by digestion with ribonuclease T₁ and T₂, alkaline phosphatase, snake venom phosphodiesterase, and nucleotide pyrophosphatase and analysis of the products by high voltage paper electrophoresis, indicated the presence of the sequence m⁷G(5)ppp(5)N at the 5-end of the mRNA. Ribonuclease T₁ and A digests of the terminally labeled, and also of unlabeled mRNA followed by fractionation on denaturing polyacrylamide gels indicated the presence of polyadenylate tracts ranging in size from 45 to 165 nucleotides at the 3-end of the mRNA.     

Conservation of reference strains of Fusarium in pure culture

More than 300 reference strains representing 60 species and varieties ofFusarium cultures named according to different taxonomic systems are currently maintained at the American Type Culture Collection (ATCC). They have been preserved by freeze-drying and by freezing and subsequent storage in liquid nitrogen (–196°C) to insure their viability without contamination, variation, mutation, or deterioration. The materials and procedures used at the ATCC for the acquisition, accessioning, cataloguing, preservation and distribution are described. Longevity storage data for the strains available for distribution are presented and discussed.     

Spin-trapping of the trichloromethyl radical produced during enzymic NADPH oxidation in the presence of carbon tetrachloride or bromotrichloromethane.

Utilizing the spin-trapping agent phenyl-t-butyl nitrone, a free radical has been detected which is produced from carbon tetrachloride or bromotrichloromethane during the enzymic oxidation of NADPH by rat liver microsomes. The presence of NADPH is obligatory for generation of the radical. The formation of the trichloromethyl radical-phenyl-t-butyl nitrone adduct is an enzymic process, as evidenced by the inhibition of its formation in systems containing heated microsomes and in systems containing p-hydroxymercuribenzoate. A computer-simulated ESR spectrum for the trichloromethyl adduct of phenyl-t-butyl nitrone can reproduce the essential features of the spectrum of the spin-trapped radical produced enzymically from CCl4. A mechanism is proposed for the formation of the trichloromethyl radical from CCl4 or BrCCl3.     

Selective ion binding and membrane activity of synthetic cyclopeptides

Four cyclic peptides related to the membrane-active complexones PV, cyclo-(L-Pro-Lval-D-Pro-D-Val)3, and valinomycin were synthesized: (1) cyclo-(L-Pro-L-Ala-D-Val)3 or PVPA, (2) cyclo-(L-Ala-L-Val-D-Pro-D-Val)3 or PVAV, (3) cyclo-(L-Pro-L-Val-D-Pro-D-Val)2-L-Pro-D-Val or PV-10, (4) cyclo-(L-Pro-L-Val-D-Pro-D-Val)2 or PV-8. In a two-phase extraction assay the affinity of PV and PVPA for alkali picrates was about three orders or magnitude greater than that of valinomycin. It was about equal to valinomycin for PVAV and much lower for PV-10 and PV-8. PV, PVPA and PVAV showed a selectivity sequence similar to that of valinomycin, namely K+ approximately Rb+ greater than Cs+ greater than Na+ greater than Li+. In the series PV, PV-10, PV-, the preference for K+ over Na+ was 700, 5 and less than 1, respectively. Thus, it was possible to reverse the selectivity of PV for K+ over Na+ by reducing the ring size from 12 to 8 amino acid residues. In sheep red cell lipid bilayer membranes PVPA increased the membrane conductance significantly in the presence of either KCl or NaCl but it was less potent than PV. PV-10, PV-8 and PVAV on the other hand were ineffective in this assay. The inactivity of PVAV as a potassium carrier in membrane was in contrast to its high affinity for potassium picrate in two-phase assays. Such a behaviour may be observed of a compound that has too low an aqueous cation binding constant to use the solution-complexation mechanism of PV (Davis et al. (1976) Biochemistry 15, 768--774 and Pinkerton et al. (1969) Biochem. Biophys. Res. Commun. 35, 512--518) and too slow binding and release kinetics to use the interfacial-complexation mechanism of valinomycin.     

Transdetermination of Drosophila imaginal discs cultured in vitro

Imaginal discs of Drosophila melanogaster undergo transdetermination when cultured in vivo in the abdominal cavity of adult female hosts. We report here that leg discs cultured in vitro, in a recently developed system, also undergo transdetermination. Whether cultured in vivo or in vitro, leg discs produce a similar range of specific transdetermined structures. Moreover, in comparison to discs cultured in vivo, the discs cultured in vitro exhibit a similar correlation between the amount of growth and the total frequency of transdetermination.     

Halogenated monoterpenes of the red alga Microcladia

The red marine algae Microcladia borealis, M. californica and M. coulteri produce several unusual halogenated monoterpenes including violacene, plocamene-B, plocamene-C, and plocamane-D. The isolation of these terpenes along with a study of their variation in each Microcladia at different locations are described.     

Lipid molecular motion and enzyme activity in sarcoplasmic reticulum membrane.

In biochemically active sarcoplasmic reticulum vesicles (SR) the physical state of the membrane lipids was studied by high angle x-ray diffraction and proton nuclear magnetic resonance (NMR) at 220 MHz, and related to thermal effects observed in SR functional parameters. It is shown by high angle x-ray diffraction that even at temperatures as low as 1 degree C nearly all the SR lipid hydrocarbon chains are in a disordered conformation and only a very small part (less than 3%) are in rigid crystalline order. Consistent with this observation, the NMR data indicate that the majority of SR phospholipid molecules are in a state of restricted anisotropic motion having no apparent crystalline order at temperatures as low as 5 degrees C. At this temperature most of the resonance signal is contained in a broad feature-less line of 700-Hz half-width. On the other hand, as the temperature is raised, high-resolution NMR signals, representing groups with highly isotropic motion, begin to grow in intensity. It is estimated that by 35 degrees C 90-100% of the phosphatidylcholine N-methyl protons and 35% of the hydrocarbon-chain protons give high-resolution signals. Concurrent studies on functional parameters reveal thermal effects giving rise to nonlinear Arrhenius plots for the rates of calcium transport and calcium activated ATPase. The thermal effects observed on functional parameters and on the character of phospholipid molecular motion exhibit a parallel behavior, suggesting a relationship between enzyme activity and the physical state of the membrane lipids.