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Entire Molecule (entire + molecule)
Selected AbstractsIdentification of the agent from Lactobacillus plantarum KFRI464 that enhances bacteriocin production by Leuconostoc citreum GJ7JOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2007J.Y. Chang Abstract Aim:, To provide evidence that the production of bacteriocin by lactic acid bacteria can be enhanced by the presence of a bacteriocin-sensitive strain and identify the agent that is responsible for enhancing bacteriocin production. Methods and Results:, One bacteriocin-producing lactic acid bacterium was isolated from kimchi. The strain GJ7 was designated as Leuconostoc citreum GJ7 based on Gram staining, biochemical properties, and 16S rRNA gene sequencing. The isolate produced a heat- and pH-stable bacteriocin (kimchicin GJ7), which has antagonistic activity against a broad spectrum of micro-organisms. Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis of purified kimchicin GJ7 showed a single band of molecular weight c. 3500 Da. Cultures of Leuc. citreum GJ7 in the presence of thermally inactivated kimchicin GJ7-sensitive strains, Lactobacillus plantarum KFRI 464, Lactobacillus delbrueckii KFRI 347, or Leuconostoc mesenteroides KCTC 1628, increased bacteriocin production. This inducing factor was characterized and purified from Lact. plantarum KFRI 464, which showed the greatest enhancement of kimchicin GJ7 activity. The inducing factor was purified using a DEAE (diethyl aminoethyl)-Sephacel column and high-performance liquid chromatography, and yielded a single band of c. 6500 Da. N -terminal sequencing of the inducing factor identified 16 amino acids. The N -terminal sequence of the inducing factor was synthesized and examined for the induction of kimchicin GJ7 activity, and was found to induce activity, but at a level about 10% lower than that of the entire molecule. Conclusions:, The presence of a bacteriocin-sensitive strain, Lact. plantarum KFRI 464, acts as an environmental stimulus to activate the production of kimchicin GJ7 by Leuc. citreum GJ7. The inducing factor from Lact. plantarum KFRI 464 is highly homologous to the 30S ribosomal protein S16 from various micro-organisms. The N -terminal sequence of the inducing factor examined in this study is a very important sequence related to the inducing activity. Nevertheless, the inducing factor may not be part of the ribosomal protein S16 itself. Significance and Impact of the Study:, We believe that the present study is the first to identify an agent that is produced by one micro-organism and influences bacteriocin production in another. The bacteriocin-enhancing system described in this study could be effectively used to control the growth of other micro-organisms (sensitive cells) in food systems. Moreover, this enhancement of bacteriocin production can be applied usefully in industrial production of natural food preservatives. [source] Intramolecular electronic communication in a dimethylaminoazobenzene,fullerene C60 dyad: An experimental and TD-DFT studyJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 6 2010K. Senthil Kumar Abstract An electronically push,pull type dimethylaminoazobenzene,fullerene C60 hybrid was designed and synthesized by tailoring N,N -dimethylaniline as an electron donating auxochrome that intensified charge density on the ,-azonitrogen, and on N -methylfulleropyrrolidine (NMFP) as an electron acceptor at the 4 and 4, positions of the azobenzene moiety, respectively. The absorption and charge transfer behavior of the hybrid donor-bridge-acceptor dyad were studied experimentally and by performing TD-DFT calculations. The TD-DFT predicted charge transfer interactions of the dyad ranging from 747 to 601 nm were experimentally observed in the UV-vis spectra at 721 nm in toluene and dichloromethane. A 149 mV anodic shift in the first reduction potential of the NN group of the dyad in comparison with the model aminoazobenzene derivative further supported the phenomenon. Analysis of the charge transfer band through the orbital picture revealed charge displacement from the n(NN) (nonbonding) and , (NN) type orbitals centered on the donor part to the purely fullerene centered LUMOs and LUMO+n orbitals, delocalized over the entire molecule. The imposed electronic perturbations on the aminoazobenzene moiety upon coupling it with C60 were analyzed by comparing the TD-DFT predicted and experimentally observed electronic transition energies of the dyad with the model compounds, NMFP and (E)-N,N -dimethyl-4-(p-tolyldiazenyl)aniline (AZNME). The n(NN) , ,*(NN) and ,(NN) , ,*(NN) transitions of the dyad were bathochromically shifted with a significant charge transfer character. The shifting of ,(NN) , ,*(NN) excitation energy closer to the n , ,*(NN) in comparison with the model aminoazobenzene emphasized the predominant existence of charge separated quinonoid-like ground state electronic structure. Increasing solvent polarity introduced hyperchromic effect in the ,(NN) , ,*(NN) electronic transition at the expense of transitions involved with benzenic states, and the extent of intensity borrowing was quantified adopting the Gaussian deconvolution method. On a comparative scale, the predicted excitation energies were in reasonable agreement with the observed values, demonstrating the efficiency of TD-DFT in predicting the localized and the charge transfer nature of transitions involved with large electronically asymmetric molecules with HOMO and LUMO centered on different parts of the molecular framework. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 [source] Enhanced post-source decay and cross-ring fragmentation of oligosaccharides facilitated by conversion to amino derivativesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 13 2004Jan Muzikar Post-source decay (PSD) fragmentation of chemically or enzymatically produced aminoglycans has been evaluated through matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Conversion of native glycans to their respective aminoglycan derivatives improved detection sensitivity of the usual fragments and promoted cross-ring fragmentation of linear oligosaccharides, facilitating linkage recognition. The cross-ring fragmentations for both dextrin and dextran oligosaccharides were not limited to the reducing-end glucose moiety, as they were extended throughout the entire molecule. When the amino group was generated for N-glycans derived from three different glycoproteins, an enhancement of PSD was observed, without a significant extent of cross-ring fragmentation. Copyright © 2004 John Wiley & Sons, Ltd. [source] Molecular Recognition and Crystal Energy Landscapes: An X-ray and Computational Study of Caffeine and Other MethylxanthinesCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2005Lucia Carlucci Dr. Abstract We introduce a new approach to crystal-packing analysis, based on the study of mutual recognition modes of entire molecules or of molecular moieties, rather than a search for selected atom,atom contacts, and on the study of crystal energy landscapes over many computer-generated polymorphs, rather than a quest for the one most stable crystal structure. The computational tools for this task are a polymorph generator and the PIXEL density sums method for the calculation of intermolecular energies. From this perspective, the molecular recognition, crystal packing, and solid-state phase behavior of caffeine and several methylxanthines (purine-2,6-diones) have been analyzed. Many possible crystal structures for anhydrous caffeine have been generated by computer simulation, and the most stable among them is a thermodynamic, ordered equivalent of the disordered phase, revealed by powder X-ray crystallography. Molecular recognition energies between two caffeine molecules or between caffeine and water have been calculated, and the results reveal the largely predominant mode to be the stacking of parallel caffeine molecules, an intermediately favorable caffeine,water interaction, and many other equivalent energy minima for lateral interactions of much less stabilization power. This last indetermination helps to explain why caffeine does not crystallize easily into an ordered anhydrous structure. In contrast, the mono- and dimethylxanthines (theophylline, theobromine, and the 1,7-isomer, for which we present a single-crystal X-ray study and a lattice energy landscape) do crystallize in anhydrous form thanks to the formation of lateral hydrogen bonds. 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