Resonance assignments, secondary structure and topology of leukaemia inhibitory factor in solution

The chemical shift assignments and secondary structure of a murine–human chimera,MH35, of leukaemia inhibitory factor (LIF), a 180-residue protein of molecular mass 20 kDa,have been determined from multidimensional heteronuclear NMR spectra acquired on auniformly 13C,15N-labelled sample. Secondary structure elements were defined on the basisof chemical shifts, NH-CH coupling constants, medium-range NOEs and the location ofslowly exchanging amide protons. The protein contains four -helices, the relativeorientations of which were determined on the basis of long-range, interhelical NOEs. The fourhelices are arranged in an up-up-down-down orientation, as found in other four-helical bundlecytokines. The overall topology of MH35-LIF is similar to that of the X-ray crystallographicstructure for murine LIF [Robinson et al. (1994) Cell, 77, 1101–1116]. Differencesbetween the X-ray structure and the solution structure are evident in the N-terminal tail, wherethe solution structure has a trans-Pro17 compared with the cis-Pro17 found in the crystalstructure and the small antiparallel -sheet encompassing residues in the N-terminus andCD loop in the crystal structure is less stable.     

pH inhibition of yeast ethanol fermentation in continuous culture

Summary In a low dilution rate study an unexpected pH-related inhibition of yeast fermentation was found. A higher volumetric rate of ethanol production occurred at lower pH values (2.8 to 3.2), suggesting a low optimum pH.Notation Ki product inhibition constant, L/g - Ks substrate saturation constant, g/L - P product (ethanol) concentration, g/L - S substrate (glucose) concentration, g/L - specific growth rate, h^–1 - ₀ maximum specific growth rate, h^–1     

Impact of Mt. St. Helens ashfall on fruit yield of Mountain Huckleberry,Vaccinium membranaceum,important native American food

Huckleberry plants evaluated at 13 sites in the southern Cascade Mountains of Washington State during August 1980 showed significantly lower fruit yields where subjected to heavy ash deposition following the 18 May 1980 eruption of Mt. St. Helens. High insect pollinator mortality is suspected as the major causal factor. The impact of such effects of volcanic activity on Native American subsistence is discussed.     

Studies of individual carbon sites of hen egg white lysozyme by natural abundance carbon 13 nuclear magnetic resonance spectroscopy. Assignment of the nonprotonated aromatic carbon resonances to specific residues in the sequence.

The resonances of nonprotonated aromatic carbons in natural abundance 13C NMR spectra of hen egg white lysozyme are assigned to specific residues of the amino acid sequence. Chemical shift considerations, the effect of pH, and partially relaxed Fourier transform NMR spectra are used to assign each resonance to one of the seven types of nonprotonated aromatic carbons of amino acid residues. Spectra of chemically modified lysozyme samples yield various assignments to specific residues in the sequence. Line-broadening effects caused by binding of the relaxation probes Gd3+ and 4-N-acetamido-2,2,6,6-tetramethylipiperidine-1-oxyl yield specific assignments which are fully consistent with those based on chemical modifications. The effects of paramagnetic shift reagents and amino sugar inhibitors do not yield any obvious specific assignments. The effect of pH on the chemical shift of Cgamma of His-15 yields a pKalpha in agreement with published values, and indicates that the imidazole form of His-15 exists mainly (or entirely) as the Nepsilon3-H tautomer. The effect of pH on the chemical shifts (measured up to pH 8.8, at 38 degrees) of Czeta and Cgamma of the 3 tyrosine residues yields crude pKalpha values of 9.5 and 10 for Tyr-23 and one of the other tyrosines, respectively. The 3rd tyrosine residue does not exhibit titration behavior.     

Influence of gender and castration on liver and CNS N-demethylation of morphine in rats1

Rats were injected with combinations of morphine-N-¹⁴CH₃ and morphine-6³H and the isotope content of the brain and liver was measured by combustion in a tissue oxidizer. The liver of intact male rats showed a significant increase in the ³H to ¹⁴C isotope ratio relative to the blood reflecting the existence of N-demethylation in this organ. This increase was not observed in the liver of either intact females or castrated males or females. Centrally, the hypothalamus, medial thalamus, and corpus striatum of both intact and castrated male and female rats exhibited increases in ³H to ¹⁴C isotope ratios indicating the presence of N-demethylation in these tissues. These results indicate that testicular hormones serve to increase the hepatic N-demethylation of morphine, but apparently reduce the comparable reaction in the CNS.     

An investigation of the sources of nonuniqueness in deterministic identifiability

While a choice of techniques exists for checking the deterministic (structural) identifiability of a specific linear, time-invariant model from a specific experiment, and some progress has been made towards topological criteria for identifiability, no method at present available allows quick and reliable checking of a range of models for globally unique identifiability from a range of experiments. Even individual cases are sometimes difficult and tedious to check. The reasons are examined by exhaustive case-by-case analysis of single-input experiments on all possible three-compartment models. All patterns of loss to the environment are covered, and all combinations of observed compartments. Catalogues of minimal observation sets for globally unique identifiability, and of nonuniquely identifiable cases, are presented. The structural causes of nonuniqueness are discussed by reference to examples from the latter catalogue. Methods are given for shortening the derivation of the structural equations giving rise to nonunique parameters. From the diversity of behavior found, it is concluded that the prospects of obtaining a comprehensive set of necessary and sufficient structural conditions for globally unique identifiability are poor.     

The brief survival of free-ranging baboon infants (Papio cynocephalus) after separation from their mothers

The importance of mother — infant attachment in free-ranging primates is illustrated by events culminating in the deaths of two baboon infants a few days after losing their mothers. These two cases are contrasted with those of a severely injured infant, not separated from its mother, which lived, and an animal which lost and refound its troop. Protective behavior of adult males is described. In captivity, separation sometimes produces infant depression; in nature, such depression may be fatal.     

Inhibition of cyclopropane fatty acid synthase by sinefungin and A9145C

Sinefungin and A9145C, antifungal antibiotic analogs of S-adeno-sylmethionine isolated from $\text{Streptomyces}\text{,}\text{griseolus}$, have been found to be very effective $\text{in}\text{,}\text{vitro}$ inhibitors of cyclopropane fatty acid synthase from $\text{Lactobacillus}\text{,}\text{plantarum}$. Both compounds exhibit linear competitive inhibition with a K_i for Sinefungin of 220 nM and a K_i for A9145C of 11 nM.     

Factors controlling the upper limits of fucoid algae on the shore

Year-round observations on the condition of intertidal seaweeds growing in situ on the shore, show that the upper limits of the zones characterized by Pelvetia canaliculata (L.) Done et Thur., Fucus spiralis L. and Ascophyllum nodosum (L.) Le Jol. were periodically pruned back by environmental conditions. The uppermost plants of each species showed clear signs of tissue damage 21 to 28 days after a time when drying conditions coincided with neap tides which exposed the plant to aerial conditions for long periods. High air temperatures aggravated the damage, but neither frost nor prolonged rain had any obvious adverse effects. On spring tides the plants were wetted every day and no damage resulted regardless of the weather.These species clearly all reach up to their physiological limits on the shore investigated, but presumably Fucus vesiculosus L. and F. serratus L. do not, for they were never observed to show signs of tissue damage attributable to exposure to air. Transplant experiments did, however, prove that F. serratus cannot survive in the F. spiralis zone and nor can F. spiralis persist in the Pelvetia canaliculata zone.Laboratory experiments also demonstrated that the ability to tolerate desiccation and then to resume photosynthesis and growth when re-submerged was greatest in P. canaliculata, the species found highest on the shore, and was progressively less in species inhabiting successively lower levels.