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51.
D. Cotter D.C. Hanna B. Luther-Davies R.C. Smith A.J. Turner 《Optics Communications》1974,11(1):54-56
Phase-matched backward-wave down-conversion has been obtained in the medium infrared using proustite (Ag3AsS3) as the mixing crystal. A transmission window between the two-photon lattice band and the high-frequency wing of the reststrahlen permitted 18.6 μm infrared to be generated by mixing the output of a ruby laser with stimulated Raman emission from bromoform (CHBr3). 相似文献
52.
Lantibiotics are ribosomally-synthesised antimicrobial peptides produced by Gram-positive bacteria that are characterised by the presence of lanthionine and/or methyllanthionine residues. Other unusual post-translationally modified amino acids, most frequently dehydroalanine and dehydrobutyrine, can also be present. While it has been frequently suggested that these peptides have the potential to be utilised in a wide range of medical applications, to date no actual therapeutic applications have been convincingly described. More recently, however, they have been the focus of much attention as a consequence of improved biotechnological capabilities, an improved understanding of lantibiotic biosynthesis and mode of action, and their high specific activity against multi-drug resistant bacteria. This review concerns the fundamental analyses that have revealed the importance of individual amino acids in these peptides and has permitted the implementation of rational mutagenesis strategies ('intelligenetics') to alter individual residues with a view to ultimately widening the active pH range, improve stability, and enhance binding to cell wall targets with the ultimate aim of optimising their antimicrobial activity. It is hoped that as a consequence of this improved knowledge the most suitable application of individual lantibiotics will become apparent. It should also prove possible, in the near future, to generate tailor-made lantibiotics and utilise biosynthetic enzymes to incorporate modified amino acids into non-lantibiotic peptides. In the shorter term, the extensive characterisation of lantibiotics will be instrumental in reassuring drug industry regulators of their safety and facilitate the widespread application of these novel antimicrobial agents in medicine. 相似文献
53.
Miniaturized time-of-flight mass spectrometer for peptide and oligonucleotide analysis 总被引:1,自引:0,他引:1
A matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometer was developed which uses a novel reflectron composed of a grounded cylinder and an adjustable endcap electrode to provide high-order kinetic energy focusing for a miniaturized mass analyzer. The nearly quadratic potential form of the reflecting field focuses ions desorbed from a source of very small dimensions formed by placing the sample probe within the centered hole of the coaxial dual channel plate detector. At the same time, the depth of the reflectron can be adjusted to accommodate a short drift length between the source/detector and the reflectron. For larger drift lengths, in particular to allow the addition of an XY stage for the analysis of sample arrays, endcap reflectron focusing can be combined with time-delayed ion extraction to achieve good mass resolution. The instrument has been used for the analysis of peptides digested with trypsin or carboxypeptidase, and also small DNA oligomers. 相似文献
54.
Tobacco is widely used as a model plant for feasibility studies of recombinant protein production from transgenic plants. However, dealing with large quantities of biomass to recover recombinant proteins is a challenge for down-stream processing. In this study, the effect of isoelectric precipitation on native tobacco protein was first studied. Among the three acids studied, hydrochloric acid is shown to be more effective than acetic or citric acid, and at pH 4, 60% of native tobacco protein was precipitated by HCl. Egg white lysozyme was used as the model protein to test the feasibility of polyelectrolyte precipitation in protein recovery from tobacco extract. Precipitation of lysozyme at pH 7 was shown ineffective probably because of the interference of polyphenolic acids. However, after isoelectric precipitation at pH 5 poly(acrylic) acid (PAA) was shown to precipitate 85% of the soluble lysozyme when the polymer dosage was increased to 1.5 mg polymer/mg lysozyme, while negligible amounts of native tobacco protein was co-precipitated. Lysozyme precipitation by PAA in tobacco extract obtained at pH 5 was also studied, and lysozyme yield was significant improved. 相似文献
55.
Improved procedures for N-terminal sulfonation of peptides for matrix-assisted laser desorption/ionization post-source decay peptide sequencing 总被引:3,自引:0,他引:3
Post source decay (PSD) analysis of precursor ions generated from matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry is a powerful tool for amino acid sequencing and primary structure analysis of proteins. N-Terminal sulfonation has become an effective derivatization strategy in facilitating de novo peptide sequencing by the formation of predominate y-type ion series in MALDI PSD spectra. Recently, an effective and inexpensive N-terminal derivatization method has been reported using 4-sulfophenyl isothiocyanate (SPITC) as the derivatization reagent (J. Mass. Spectrom. 2003; 38: 373-377). In this paper, we report an improvement in the derivatization procedure with this reagent that involves replacing an organic co-reagent with other chemicals and eliminating the use of organic solvent. The method is demonstrated on a model peptide and on tryptic digests of two proteins. The results indicate that the improved sulfonation reaction can be implemented with high efficiency under aqueous conditions and that the sensitivity of mass detection can be increased considerably. 相似文献
56.
Megan Hogan Juliet Cotter James Claffey Brendan Gleeson Denise Wallis Donal O'Shea Matthias Tacke 《Helvetica chimica acta》2008,91(9):1787-1797
From the carbolithiation of 1‐(cyclopenta‐2,4‐dien‐1‐ylidene)‐N,N‐dimethylmethanamine (=6‐(dimethylamino)fulvene; 3 ) and different lithiated azaindoles 2 (1‐methyl‐7‐azaindol‐2‐yl, 1‐[(diethylamino)methyl]‐7‐azaindol‐2‐yl, and 1‐(methoxymethyl)‐7‐azaindol‐2‐yl), the corresponding lithium cyclopentadienide intermediates 4a – 4c were formed (7‐azaindole=1H‐pyrrolo[2,3‐b]pyridine). The latter underwent a transmetallation reaction with TiCl4 resulting in the (dimethylamino)‐functionalised ‘titanocenes’ 5a – 5c . When the ‘titanocenes’ 5a – 5c were tested against LLC‐PK cells, the IC50 values obtained were of 8.8, 12, and 87 μM , respectively. The most cytotoxic ‘titanocene’, 5a , with an IC50 value of 8.8 μM is nearly as cytotoxic as cis‐platin, which showed an IC50 value of 3.3 μM when tested on the epithelial pig kidney LLC‐PK cell line, and ca. 200 times better than ‘titanocene dichloride’ itself. 相似文献
57.
Marzilli LA Golden TR Cotter RJ Woods AS 《Journal of the American Society for Mass Spectrometry》2000,11(11):1000-1008
We present the use of Pronase digestion and in-source decay in the presence of ammonium sulfate as complementary techniques to confirm the amino acid sequence of a peptide. Pronase, a commercial preparation from Streptomyces griseus, is a combination of proteolytic enzymes. It produces carboxypeptidase and aminopeptidase ladders using a single Pronase digestion and represents an inexpensive, nonspecific, and fast supplement to traditional sequencing enzymes. However, N-terminal peptidase activity appears dependent on the terminal amino acid residue. We also introduce the use of saturated ammonium sulfate as an "on-slide" sample additive to promote in-source fragmentation of peptides. Use of saturated ammonium sulfate resulted in a simple way to increase peptide backbone fragmentation and essentially produced either a cn or yn ion series. Together these techniques provide useful supplements to existing methods for peptide sequence information. 相似文献
58.
59.
SL Mironov E Skorova G Taschenberger N Hartelt VO Nikolaev MJ Lohse S Kügler 《BMC neuroscience》2009,10(1):29-11
Background
cAMP is an ubiquitous second messenger mediating various neuronal functions, often as a consequence of increased intracellular Ca2+ levels. While imaging of calcium is commonly used in neuroscience applications, probing for cAMP levels has not yet been performed in living vertebrate neuronal tissue before. 相似文献60.