The accurate crystal structure determinations of MeCbl (1), CNCbl.2LiCl (2), and CNCbl.KCl (3), based on synchrotron diffraction data collected at 100 K and using high-quality single crystals, are reported. Refinements gave R1 indices of 0.0834 (1), 0.0434 (2), and 0.0773 (3). The influence of the water of crystallization and ion content on the crystal packing of these and other cobalamins (XCbl) is discussed, and a relationship between the crystal packing and the corrin side chain conformations is presented. An analysis of the bond lengths within the corrin moiety, based on 13 accurate structures with several X groups, shows that the trend of the C-C and C-N distances can be interpreted in terms of electronic and steric factors. The variation in structural, NMR and IR spectroscopic, and electrochemical properties are compared with those of cobaloximes, the B12 model, when X is varied. This comparison indicates that the pi-back-donation from metal to the CN axial ligand and the transmission of the trans influence of the X ligand are more effective in cobalamins than in cobaloximes. These findings are consistent with a significantly greater availability of electron charge on Co in cobalamins, and, hence, a semiquantitative evaluation of the electronic difference between the cobalt centers in the two systems is allowed.
In the computation of synthetic seismograms by modal summation, when a medium with a sharp lateral discontinuity is considered, a fundamental role is played by a coupling coefficient cj#, The coefficient r;ir is defined via an integral relation involving products between displacements and stresses and can be evaluated both numerically and analytically. The calculation of r;i. can be reduced to the analytical computation of a sum of integrals of elementary functions. The analytical method proved to be particularly convenient for its speed and precision of the results obtained.The energy redistribution within the different modes is illustrated, both in the frequency and in the time domain. Mode conversion cannot be neglected when dealing with higher modes.
High-resolution X-ray structure determinations of chloro- and azidocobalamin·2LiCl, crystallized from concentrated aqueous LiCl solutions, show lithium cations coordinated to the phosphate O atom and to the amidic O atoms of the corrin side chains, and chloride anions held by H-bonds to the corrin amidic N atoms. The structures of the two compounds represent the first structural picture of the interactions of the cobalamin molecule with ionic species.
OriginalAntimicrobial and host cell-directed activities of Gly/Ser-rich peptides from salmonid cathelicidins This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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3Highlights 38• Salmonid cathelicidin-derived peptides show medium-sensitive antimicrobial activity 39• They are not cytotoxic to fish cells and promote proliferation of trout fibroblasts 40• Peptide STF(1-37) potentiates phagocytosis and respiratory burst in trout leukocytes 41• STF(1-37) and β-glucan act synergistically to immunostimulate trout leukocytes 42Cathelicidins, a major family of vertebrate antimicrobial peptides (AMPs), have a recognized role 44 in the first line of defense against infections. They have been identified in several salmonid species, 45 where the putative mature peptides are unusually long and rich in serine and glycine residues, often 46 arranged in short multiple repeats (RLGGGS/RPGGGS) intercalated by hydrophobic motifs. 47Fragments of 24 to 40 residues, spanning specific motifs and conserved sequences in grayling or 48 brown, rainbow and brook trout, were chemically synthesized and examined for antimicrobial 49 activity against relevant Gram-positive and Gram-negative salmonid pathogens, as well as 50 laboratory reference strains. They were not active in complete medium, but showed varying potency 51 and activity spectra in diluted media. Bacterial membrane permeabilization also occurred only 52 under these conditions and was indicated by rapid propidium iodide uptake in peptide-treated 53 bacteria. However, circular dichroism analyses indicated that they did not significantly adopt 54 ordered conformations in membrane-like environments. The peptides were not hemolytic or 55 cytotoxic to trout cells, including freshly purified head kidney leukocytes (HKL) and the 56 fibroblastic RTG-2 cell line. Notably, when exposed to them, HKL showed increased metabolic 57 activity, while a growth-promoting effect was observed on RTG-2 cells, suggesting a functional 58 interaction of salmonid cathelicidins with host cells similar to that shown by mammalian ones. The 59 three most active peptides produced a dose-dependent increase in phagocytic uptake by HKL 60 simultaneously stimulated with bacterial particles. The peptide STF(1-37), selected for further 61 analyses, also enhanced phagocytic uptake in the presence of autologous serum, and increased 62 intracellular killing of live E. coli. Furthermore, when tested on HKL in combination with the 63 immunostimulant β-glucan, it synergistically potentiated both phagocytic up...
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