We present some interesting connections between PT symmetry and conformal symmetry. We use them to develop a metricated theory of electromagnetism in which the electromagnetic field is present in the geometric connection. However, unlike Weyl who first advanced this possibility, we do not take the connection to be real but to instead be PT symmetric, with it being \(iA_{\mu }\) rather than \(A_{\mu }\) itself that then appears in the connection. With this modification the standard minimal coupling of electromagnetism to fermions is obtained. Through the use of torsion we obtain a metricated theory of electromagnetism that treats its electric and magnetic sectors symmetrically, with a conformal invariant theory of gravity being found to emerge. An extension to the non-Abelian case is provided. 相似文献
An effective approach to the model VUQ process by means of direct collaboration between computationalist and experimental data analyst is proposed. An analysis of data from a laminar helium plume experiment provides a demonstration of the proposed collaboration process. Consistency analysis serves a central role in the collaboration. It takes the data and uncertainties from both analyst and computationalist and provides an objective and quantifiable measure of agreement between the two. Despite the simplicity of the laminar helium system and the computational model, certain phenomena brought to light in the collaboration process make it difficult to find quantitative agreement in the data. These phenomena include the unsteady behavior of air flow in an open room, and the presence of helium permeation to the region near the plume. Important sources of error in the simulation include uncertainty in the room temperature (295.15 to 305.15 K), uncertainty in the helium inlet velocity (0.1215 \(\frac {m}{s}\) to 0.1415 \(\frac {m}{s}\)), and uncertainty in local helium permeation (0 % to 3 % by mass.) The collaboration process allows for a better understanding of the phenomena affecting the plume and the relative sensitivies of the system to these phenomena. 相似文献
Tubulin, which is the building block of microtubules, plays an important role in cell division. This critical role makes tubulin an attractive target for the development of chemotherapeutic drugs to treat cancer. Currently, there is no general binding assay for tubulin–drug interactions. The present work describes the application of the catch-and-release electrospray ionization mass spectrometry (CaR-ESI-MS) assay to investigate the binding of colchicinoid drugs to αβ-tubulin dimers extracted from porcine brain. Proof-of-concept experiments using positive (ligands with known affinities) and negative (non-binders) controls were performed to establish the reliability of the assay. The assay was then used to screen a library of seven colchicinoid analogues to test their binding to tubulin and to rank their affinities.
The membrane‐proximal external region (MPER) of HIV gp41 is an established target of antibodies that neutralize a broad range of HIV isolates. To evaluate the role of the transmembrane (TM) domain, synthetic MPER‐derived peptides were incorporated into lipid nanoparticles using natural and designed TM domains, and antibody affinity was measured using immobilized and solution‐based techniques. Peptides incorporating the native HIV TM domain exhibit significantly stronger interactions with neutralizing antibodies than peptides with a monomeric TM domain. Furthermore, a peptide with a trimeric, three‐helix bundle TM domain recapitulates the binding profile of the native sequence. These studies suggest that neutralizing antibodies can bind the MPER when the TM domain is a three‐helix bundle and this presentation could influence the binding of neutralizing antibodies to the virus. Lipid‐bilayer presentation of viral antigens in Nanodiscs is a new platform for evaluating neutralizing antibodies. 相似文献
The calcium-dependent antibiotic (CDA), from Streptomyces coelicolor, is an acidic lipopeptide comprising an N-terminal 2,3-epoxyhexanoyl fatty acid side chain and several nonproteinogenic amino acid residues. S. coelicolor grown on solid media was shown to produce several previously uncharacterized peptides with C-terminal Z-dehydrotryptophan residues. The CDA biosynthetic gene cluster contains open reading frames encoding nonribosomal peptide synthetases, fatty acid synthases, and enzymes involved in precursor supply and tailoring of the nascent peptide. On the basis of protein sequence similarity and chemical reasoning, the biosynthesis of CDA is rationalized. Deletion of SCO3229 (hmaS), a putative 4-hydroxymandelic acid synthase-encoding gene, abolishes CDA production. The exogenous supply of 4-hydroxymandelate, 4-hydroxyphenylglyoxylate, or 4-hydroxyphenylglycine re-establishes CDA production by the DeltahmaS mutant. Feeding analogs of these precursors to the mutant resulted in the directed biosynthesis of novel lipopeptides with modified arylglycine residues. 相似文献
A method to prepare α,α-acyl amino acid derivatives efficiently by Cu(OTf)(2) +1,10-phenanthroline (1,10-phen)-catalyzed amination of 1,3-dicarbonyl compounds with PhI?NSO(2) Ar is described. The mechanism is thought to initially involve aziridination of the enolic form of the substrate, formed in situ through coordination to the Lewis acidic metal catalyst, by the putative copper-nitrene/imido species generated from the reaction of the metal catalyst with the iminoiodane source. Subsequent ring opening of the resultant aziridinol adduct under the Lewis acidic conditions then provided the α-aminated product. The utility of this method was exemplified by the enantioselective synthesis of a precursor of 3-styryl-2-benzoyl-L-alanine. 相似文献