Experimental and theoretical studies on organic D-π-A systems containing three-coordinate boron moieties as both π-donor and π-acceptor

Four linear π-conjugated systems with 1,3-diethyl-1,3,2-benzodiazaborolyl [C(6)H(4)(NEt)(2)B] as a π-donor at one end and dimesitylboryl (BMes(2)) as a π-acceptor at the other end were synthesized. These unusual push-pull systems contain phenylene (-1,4-C(6)H(4)-; 1), biphenylene (-4,4'-(1,1'-C(6)H(4))(2)-; 2), thiophene (-2,5-C(4)H(2)S-; 3), and dithiophene (-5,5'-(2,2'-C(4)H(2)S)(2)-; 4) as π-conjugated bridges and different types of three-coordinate boron moieties serving as both π-donor and π-acceptor. Molecular structures of 2, 3, and 4 were determined by single-crystal X-ray diffraction. Photophysical studies on these systems reveal blue-green fluorescence in all compounds. The Stokes shifts for 1, 2, and 3 are notably large at 7820-9760 cm(-1) in THF and 5430-6210 cm(-1) in cyclohexane, whereas the Stokes shift for 4 is significantly smaller at 5510 cm(-1) in THF and 2450 cm(-1) in cyclohexane. Calculations on model systems 1'-4' show the HOMO to be mainly diazaborolyl in character and the LUMO to be dominated by the empty p orbital at the boron atom of the BMes(2) group. However, there are considerable dithiophene bridge contributions to both orbitals in 4'. From the experimental data and MO calculations, the π-electron-donating strength of the 1,3-diethyl-1,3,2-benzodiazaborolyl group was found to lie between that of methoxy and dimethylamino groups. TD-DFT calculations on 1'-4', using B3LYP and CAM-B3LYP functionals, provide insight into the absorption and emission processes. B3LYP predicts that both the absorption and emission processes have strong charge-transfer character. CAM-B3LYP which, unlike B3LYP, contains the physics necessary to describe charge-transfer excitations, predicts only a limited amount of charge transfer upon absorption, but somewhat more upon emission. The excited-state (S(1)) geometries show the borolyl group to be significantly altered compared to the ground-state (S(0)) geometries. This borolyl group reorganization in the excited state is believed to be responsible for the large Stokes shifts in organic systems containing benzodiazaborolyl groups in these and related compounds.     

Engineering of Cysteine Residues Leads to Improved Production of a Human Dipeptidase Enzyme in <Emphasis Type="Italic">E. coli</Emphasis>

Low yields, poor folding efficiencies and improper disulfide bridge formation limit large-scale production of cysteine-rich proteins in Escherichia coli. Human renal dipeptidase (MDP), the only human β-lactamase known to date, is a homodimeric enzyme, which contains six cysteine residues per monomer. It hydrolyses penem and carbapenem β-lactam antibiotics and can cleave dipeptides containing amino acids in both d- and l-configurations. In this study, MDP accumulated in inactive form in high molecular weight, disulfide-linked aggregates when produced in the E. coli periplasm. Mutagenesis of Cys361 that mediates dimer formation and Cys93 that is unpaired in the native MDP led to production of soluble recombinant enzyme, with no change in activity compared with the wild-type enzyme. The removal of unpaired or structurally inessential cysteine residues in this manner may allow functional production of many multiply disulfide-linked recombinant proteins in E. coli.     

Association of Increased Sun Exposure Over the Life‐course with a Reduced Risk of Juvenile Idiopathic Arthritis

Cutaneous sun exposure is an important determinant of circulating vitamin D. Both sun exposure and vitamin D have been inversely associated with risk of autoimmune disease. In juvenile idiopathic arthritis (JIA), low circulating vitamin D appears common, but disease‐related behavioral changes may have influenced sun exposure. We therefore aimed to determine whether predisease sun exposure is associated with JIA. Using validated questionnaires, we retrospectively measured sun exposure for 202 Caucasian JIA case–control pairs born in Victoria Australia, matched for birth year and time of recruitment. Measures included maternal sun exposure at 12 weeks of pregnancy and child sun exposure across the life‐course prediagnosis. We converted exposure to UVR dose and looked for case–control differences using logistic regression, adjusting for potential confounders. Higher cumulative prediagnosis UVR exposure was associated with reduced risk of JIA, with a clear dose–response relationship (trend P = 0.04). UVR exposure at 12 weeks of pregnancy was similarly inversely associated with JIA (trend P = 0.011). Associations were robust to sensitivity analyses for prediagnosis behavioral changes, disease duration and knowledge of the hypothesis. Our data indicate that lower UVR exposure may increase JIA risk. This may be through decreased circulating vitamin D, but prospective studies are required to confirm this.     

TRPM5-expressing microvillous cells in the main olfactory epithelium

Background  

The main olfactory epithelium (MOE) in the nasal cavity detects a variety of air borne molecules that provide information regarding the presence of food, predators and other relevant social and environmental factors. Within the epithelium are ciliated sensory neurons, supporting cells, basal cells and microvillous cells, each of which is distinct in morphology and function. Arguably, the least understood, are the microvillous cells, a population of cells that are small in number and whose function is not known. We previously found that in a mouse strain in which the TRPM5 promoter drives expression of the green fluorescent protein (GFP), a population of ciliated olfactory sensory neurons (OSNs), as well as a population of cells displaying microvilli-like structures is labeled. Here we examined the morphology and immunocytochemical properties of these microvillous-like cells using immunocytochemical methods.     

Fibrewise completion and unstable Adams spectral sequences

We describe a tower of spaces whose inverse limit is a “fiberwise completion” of a fibrationE →B, and study the resulting spectral sequence converging to the homotopy groups of the space of lifts of a mapX →B. This is used to give a proof of the “generalized Sullivan conjecture”. All three authors were supported in part by the National Science Foundation.     

The visible spectrum of fulvene

Vapour phase and mixed crystal of the visible band system of fulvene are reported. The spectra show several interesting features including a main progression of 660 cm^?1 corresponding to the out-of-plane methylene twisting vibration. Strong Herzberg—Teller origins together with the breadth and overall diffuseness indicate two electronic states of symmetry A₁ and B₂ may be responsible for the observed spectrum. The spectra are blue shifted in going from the vapour to mixed crystal and show sequence structure to the blue of the main bands in the vapour phase.     

On the dimension of infinite covers

We prove the following theorem and some generalizations. . Let be a connected CW complex which satisfies Poincaré duality of dimension . For any subgroup of , let denote the cover of corresponding to . If has infinite index in , then is homotopy equivalent to an -dimensional CW complex.