Surface properties of class ii hydrophobins from Trichoderma reesei and influence on bubble stability

We report the remarkable surface behavior of class II hydrophobin proteins HFBI and HFBII from Trichoderma reesei and the resulting effect that these proteins have on the stability of air bubbles to the process of disproportionation. The surface properties were studied using surface tensiometry and surface shear rheology. Surface tensiometry data show that hydrophobins are very surface active proteins, reducing the surface tension to approximately 30 mN m-1. The rate at which the hydrophobins adsorb at the surface may also be related to the self-assembly behavior in aqueous solution. We further show that hydrophobins form air/water surfaces with high elasticity, the magnitude of which is well in excess of that of surface layers formed by other common proteins used as foam or emulsion stabilizers. The measured surface properties translate to the stability of bubbles with adsorbed hydrophobin, and in this study, we demonstrate the ability of hydrophobin to have a dramatic effect on the rate of disproportionation in some simple bubble dissolution studies.     

Nanoporous microbead supported bilayers: stability, physical characterization, and incorporation of functional transmembrane proteins

The introduction of functional transmembrane proteins into supported bilayer-based biomimetic systems presents a significant challenge for biophysics. Among the various methods for producing supported bilayers, liposomal fusion offers a versatile method for the introduction of membrane proteins into supported bilayers on a variety of substrates. In this study, the properties of protein containing unilamellar phosphocholine lipid bilayers on nanoporous silica microspheres are investigated. The effects of the silica substrate, pore structure, and the substrate curvature on the stability of the membrane and the functionality of the membrane protein are determined. Supported bilayers on porous silica microspheres show a significant increase in surface area on surfaces with structures in excess of 10 nm as well as an overall decrease in stability resulting from increasing pore size and curvature. Comparison of the liposomal and detergent-mediated introduction of purified bacteriorhodopsin (bR) and the human type 3 serotonin receptor (5HT3R) are investigated focusing on the resulting protein function, diffusion, orientation, and incorporation efficiency. In both cases, functional proteins are observed; however, the reconstitution efficiency and orientation selectivity are significantly enhanced through detergent-mediated protein reconstitution. The results of these experiments provide a basis for bulk ionic and fluorescent dye-based compartmentalization assays as well as single-molecule optical and single-channel electrochemical interrogation of transmembrane proteins in a biomimetic platform.     

Kinetics of amide formation through carbodiimide/N-hydroxybenzotriazole (HOBt) couplings

The kinetics of formation of amide, 4, from the corresponding carboxylic acid by reaction with the isopropyl ester of methionine (MIPE), mediated by carbodiimide EDCI, 1, and HOBt, 2, have been studied in 1-methyl-2-pyrrolidinone (NMP) using reaction calorimetry. The reaction rates have been found to be independent of the concentration of HOBt, showing that the rate-determining step is the reaction between the carboxylic acid and EDCI to give the corresponding O-acylisourea. The pH dependence of the observed rate constants for O-acylisourea formation is consistent with a second-order reaction between doubly protonated EDCI (EDCIH2(2+), 6) and the carboxylate group. The observed rate constants fall sharply at high pH, as the fraction of EDCI as EDCIH2(2+) continues to fall strongly, whereas the carboxylic acid group is already fully ionized. The rate constant, kP, for reaction between the carboxylate group of acid, 3, and EDCIH2(2+) has a value of kP = 4.1 x 10(4) M(-1) s(-1) at 20 degrees C, some 10(5) times higher than similar rate constants measured in water. The subsequent catalytic cycle, involving reaction of O-acylisourea with HOBt to give HOBt ester, which then reacts with the amine to give the amide with regeneration of HOBt, determines the product distribution. In the case of the amino acid, 3, reaction of the O-acylisourea with MIPE to give amide, 4, is increasingly favored at higher pH values over that with the less basic internal aromatic amine of 3 to give the diamide 5.     

A highly effective one-pot synthesis of quinolines from o-nitroarylcarbaldehydes

A highly effective one-pot Friedl?nder quinoline synthesis using inexpensive reagents has been developed. o-Nitroarylcarbaldehydes were reduced to o-aminoarylcarbaldehydes with iron in the presence of catalytic HCl (aq.) and subsequently condensed in situ with aldehydes or ketones to form mono- or di-substituted quinolines in high yields (66-100%).     

Mupirocin H, a novel metabolite resulting from mutation of the HMG-CoA synthase analogue, mupH in Pseudomonas fluorescens

Mutation of the HMG-CoA synthase encoding mupH gene in Pseudomonas fluorescens gives rise to a new metabolite formed from a truncated polyketide intermediate, providing in vivo evidence for the roles of mupH and cognate genes found in several "AT-less" and other bacterial PKS gene clusters responsible for the biosynthesis of diverse metabolites containing acetate/propionate derived side chains.     

Structural characterization of sialylated glycoforms of H. influenzae by electrospray mass spectrometry: fragmentation of protonated and sodiated O-deacylated lipopolysaccharides

Sialylated lipopolysaccharide (LPS) glycoforms from Haemophilus influenzae were characterized by tandem mass spectrometry using a new generation hyphenated mass spectrometer which combines a triple quadrupole and a linear ion trap (Q-Trap). The fragmentation of both protonated and sodiated molecular ions from O-deacylated LPS (LPS-OH) obtained in MS(2) experiments in the positive mode was studied. The MS(2) spectra of protonated ions provided unambiguous evidence for the presence and sequence of sialylated lactosamine present in lacto-N-neotetraose oligosaccharide extensions but not for sialyl-lactose structures whilst fragmentation of sodiated adducts, [M+Na](+), afforded information diagnostic of mono- and disialylated lactose extensions. To study this we used a highly sialylated LPS from a H. influenzae strain capable of sialyl-lactose expression only. We then applied the method to the H. influenzae genome strain, Rd, in which glycoforms containing both sialyl-lactose and sialyl-lacto-N-neotetraose were detected from diagnostic B-ions at m/z 638.2 ([Neu5Ac(1) Hex(2)+Na](+)) and 657.2 ([Neu5Ac(1) Hex(1) HexNAc(1)+H](+)). Unique fragmentation patterns provided the locations and sequences of these oligosaccharide extensions. This is the first time both sialylated lactose and sialylated lacto-N-neotetraose units have been detected and characterized by tandem mass spectrometry in the same molecule. This methodology is of general applicability for determination of common sialylated oligosaccharide extension in bacterial LPS.     

Search for electron neutrino appearance at the Delta m2 approximately 1 eV2 scale

The MiniBooNE Collaboration reports first results of a search for nu e appearance in a nu mu beam. With two largely independent analyses, we observe no significant excess of events above the background for reconstructed neutrino energies above 475 MeV. The data are consistent with no oscillations within a two-neutrino appearance-only oscillation model.     

Regioselective photocyclization of (e)‐2‐(2,3,6‐trichlorostyryl)‐benzothiazole and synthesis of 3,4‐dichloro‐ and 4‐chlorobenzothiazolo[3,2‐α]quinolinium chlorides: A synthetic and theoretical study

A high degree of regioselectivity is observed in the photochemically induced cyclization of (E)‐2‐(2,3,6‐trichlorostyryl)benzothiazole ( 1a ). According to the proposed mechanism, this compound was expected to afford two products, 3,4‐dichloro‐ and 1,4‐dichlorobenzothiazolo[3,2‐α]quinolinium chlorides ( 4a and 4a' , respectively). However, this reaction produced 3,4‐dichlorobenzazolo[3,2‐α]quinolinium chloride ( 4a ) as the sole product. On the other hand, irradiation of (E)‐2‐(2,3,5‐trichlorostyryl)benzothiazole ( 1b ) failed to produce the expected 1,3‐dichlorobenzothiazolo[3,2‐α]quinolinium chloride ( 4b ). Furthermore, (E)‐2,3‐difluorostrylbenzothiazole ( 1c ) also failed to give the corresponding 1‐fluorobenzothiazolo[3,2‐α]quinolinium fluoride ( 4c ). Interestingly, the irradiation of 2,6‐dichlorostyrylbenzothialole ( 1d ) produced 4‐chlorobenzothiazolo[3,2‐α]quinolinium chloride ( 4d ) in excellent yield. This paper presents the results of these investigations and a mechanistic rationale for the outcome of this reaction based on steric arguments and theoretical studies using a combination of molecular mechanics (MM+) and semiempirical quantum mechanical calculations (PM3/RHF/CI). Two‐dimensional high field nmr methods were employed to make complete assignments of the proton and carbon spectra of all new compounds.     

The Newman-Kwart rearrangement: a microwave kinetic study

The kinetic profile of the Newman-Kwart rearrangement has been evaluated using microwave heating. After first demonstrating equivalence between conventional convective heating and microwave heating, data was gathered and analyzed to determine the effects of substituent, solvent, and concentration on the reaction order. Reaction rate constants, Arrhenius constants, and activation energies have been determined. The reaction rate shows strong sensitivity to the substituent and modest sensitivity to the solvent. At high concentrations, the reaction order increases from the previously reported first-order to a mixed first/second-order reaction. Overall, this re-evaluation of the Newman-Kwart rearrangement has shown the reaction rate order to be more complex than previously thought. In addition, microwave heating has proven ideal for the rapid collection of data to facilitate this type of kinetic study.     

A Gas-phase study of the preferential solvation of Mn2+ in mixed water/methanol clusters

The kinetic shift that exists between two competing unimolecular fragmentation processes has been used to establish whether or not gas-phase Mn(2+) exhibits preferential solvation when forming mixed clusters with water and methanol. Supported by molecular orbital calculations, these first results for a metal dication demonstrate that Mn(2+) prefers to be solvated by methanol in the primary solvation shell.