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991.
Luke F. Gamon Joses G. Nathanael Bethany I. Taggert Fraser A. Henry Jana Bogena Prof. Uta Wille 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(42):14924-14930
The fragmentation–rearrangement of peptide backbones mediated by nitrogen dioxide, NO2., was explored using di‐, tri‐, and tetrapeptides 8 – 18 as model systems. The reaction, which is initiated through nonradical N‐nitrosation of the peptide bond, shortens the peptide chain by the expulsion of one amino acid moiety with simultaneous fusion of the remaining molecular termini through formation of a new peptide bond. The relative rate of the fragmentation–rearrangement depends on the nature of the amino acids and decreases with increasing steric bulk at the α carbon in the order Gly>Ala>Val. Peptides that possessed consecutive aromatic side chains only gave products that resulted from nitrosation of the sterically less congested N‐terminal amide. Such backbone fragmentation–rearrangement occurs under physiologically relevant conditions and could be an important reaction pathway for peptides, in which sections without readily oxidizable side chains are exposed to the air pollutant NO2.. In addition to NO2.‐induced radical oxidation processes, this outcome shows that ionic reaction pathways, in particular nitrosation, should be factored in when assessing NO2. reactivity in biological systems. 相似文献
992.
Microbial cell biosensors, where cells are in direct connection with a transducer enabling quantitative and qualitative detection of an analyte, are very promising analytical tools applied mainly for assays in the environmental field, food industry or biomedicine. Microbial cell biosensors are an excellent alternative to conventional analytical methods due to their specificity, rapid detection and low cost of analysis. Nowadays, nanomaterials are often used in the construction of biosensors to improve their sensitivity and stability. In this review, the combination of microbial and other individual cells with different nanomaterials (carbon nanotubes, graphene, gold nanoparticles, etc.) for the construction of biosensors is described and their applications are provided as well. 相似文献
993.
The total least squares (TLS) and truncated TLS (T-TLS) methods are widely known linear data fitting approaches, often used also in the context of very ill-conditioned, rank-deficient, or ill-posed problems. Regularization properties of T-TLS applied to linear approximation problems Ax ≈ b were analyzed by Fierro, Golub, Hansen, and O’Leary (1997) through the so-called filter factors allowing to represent the solution in terms of a filtered pseudoinverse of A applied to b. This paper focuses on the situation when multiple observations b 1,..., b d are available, i.e., the T-TLS method is applied to the problem AX ≈ B, where B = [b 1,..., b d ] is a matrix. It is proved that the filtering representation of the T-TLS solution can be generalized to this case. The corresponding filter factors are explicitly derived. 相似文献
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998.
Generation of a Genetically Encoded,Photoactivatable Intein for the Controlled Production of Cyclic Peptides
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M. Sc. Jana K. Böcker M. Sc. Kristina Friedel M. Sc. Julian C. J. Matern M. Sc. Anne‐Lena Bachmann Prof. Dr. Henning D. Mootz 《Angewandte Chemie (International ed. in English)》2015,54(7):2116-2120
Cyclic peptides are important natural products and hold great promise for the identification of new bioactive molecules. The split‐intein‐mediated SICLOPPS technology provides a generic access to fully genetically encoded head‐to‐tail cyclized peptides and large libraries thereof (SICLOPPS=split‐intein circular ligation of peptides and proteins). However, owing to the spontaneous protein splicing reaction, product formation occurs inside cells, making peptide isolation inconvenient and precluding traditional in vitro assays for inhibitor discovery. The design of a genetically encoded, light‐dependent intein using the photocaged tyrosine derivative ortho‐nitrobenzyltyrosine incorporated at an internal, non‐catalytic position is now reported. Stable intein precursors were purified from the E. coli expression host and subsequently subjected to light activation in vitro for both the regular protein splicing format and cyclic peptide production, including the natural product segetalin H as an example. The activity of the intein could also be triggered in living cells. 相似文献
999.
P. Dasgupta Y.M. Jana R. Higashinaka D. Ghosh 《Journal of Physics and Chemistry of Solids》2007,68(3):347-354
Magnetic susceptibility obtained from magnetization measurement (for fields H=0.1 and 1.0 T) of polycrystalline Eu2Ti2O7 shows two distinct features. Firstly, increases on cooling below 300 K and attains a temperature-independent constant value at 68 K (Tmax). Secondly, shows an antiferromagnetic increase below 4.9±0.1 K. The former behavior is explained by crystal field (CF) theory. CF levels and wave functions of ground and excited states are determined accurately from analyses of and earlier reported Mössbauer and optical spectra. Analysis of vs. 1/T curve at low temperatures gives the classical nearest-neighbor exchange interaction Jcl=−0.76 K and a weak dipolar interaction Dnn=0.0056 K. CP of polycrystalline sample of Eu2Ti2O7 and Y2Ti2O7 are measured between 1.8-35 and 1.8-120 K respectively and θD vs. T (K) curves are calculated. At 4 K, θD of Eu2Ti2O7 shows a kink and dCP/dT curve show a maximum. Optical results show energy exchange between Eu3+ ions at intrinsic and extrinsic (defect) sites via super-exchange interaction at low temperature which may account for the observed anomalous behavior of and CP. 相似文献
1000.
The formulae for the free energy, when the driving distributions in Generalized Random Energy Model (GREM) are of the form
for γ ≥ 1 are derived. The large deviation technique allows the use of different distributions at different levels of the
GREM. As an illustration we consider, in detail, a two level GREM with exponential and Gaussian distributions. This simple
case itself leads to interesting phenomena. 相似文献