No abstract

A direct oxo-ester peptide ligation method has been developed. Through the use of an activated C-terminal para-nitrophenyl ester (cf. 1), it is possible to achieve direct cysteine ligations (1 +2 → 4). Peptide substrates incorporating bulky C-terminal amino acids (cf. 1, R) can be accommodated with high reaction efficiency.

In this study, genomic DNA was screened from Halobacillus andaensis NEAU-ST10-40T by selection in Escherichia coli KNabc lacking three major Na+/H+ antiporters. One gene designated upf0118 exhibiting Na+(Li+)/H+ antiport activity was finally cloned. Protein alignment showed that UPF0118 shares the highest identity of 81.5% with an unannotated gene encoding a protein with uncharacterized protein function belonging to UPF0118 family from H. kuroshimensis, but shares no identity with all known specific Na+(Li+)/H+ antiporter genes or genes with Na+(Li+)/H+ antiport activity. Growth test, western blot and Na+(Li+)/H+ antiport assay revealed that UPF0118 as a transmembrane protein exhibits pH-dependent Na+(Li+)/H+ antiport activity. Phylogenetic analysis indicated that UPF0118 clustered with all its homologs belonging to UPF0118 family at a wide range of 22–82% identities with the bootstrap value of 92%, which was significantly distant with all known specific single-gene Na+(Li+)/H+ antiporters and single-gene proteins with the Na+(Li+)/H+ antiport activity. Taken together, we propose that UPF0118 should represent a novel class of Na+(Li+)/H+ antiporter. To the best of our knowledge, this is the first report on the functional analysis of a protein with uncharacterized protein function as a representative of UPF0118 family containing the domain of unknown function, DUF20.

We studied the photoluminescence from GaAsN/GaAs, with the nitrogen content of less than 0.5%. The low-temperature photoluminescence spectra are composed of several excitons bound to nitrogen complexes, each associated with different composition or configuration. These features were studied as a function of the excitation intensity, temperature, concentration, and growth conditions. The dependence of the binding energy of the dominant recombination center on the nitrogen concentration is interpreted in terms of a hierarchy of nitrogen complexes, from centers composed of at least two nitrogen atoms to more extended clusters. These excitonic transitions are very sensitive to growth parameters and can be used to study the statistical distribution of nitrogen in nominally uniform layers. We also show that the transition from nitrogen doping to alloy formation occurs for nitrogen concentrations above 0.25%.