Influence of hydrocarbon surfactant on the aggregation behavior of silicone surfactant: observation of intermediate structures in the vesicle-micelle transition

Intermediate structures of the aggregates in the aqueous solution of an ABA-type silicone surfactant and in the process of an SDS-induced vesicle-micelle transition are reported. In single ABA silicone surfactant aqueous solutions, large multilamellar vesicles (MLV), small single lamellar vesicles (SLV), threadlike micelles (TLM), and spheroidal micelles were observed. Interestingly, a large amount of TLMs were found entrapped into the large MLVs, but not in SLVs. Disintegration of the small vesicles inside the MLVs indicates that the entrapped TLM are from the disintegrated membrane of the entrapped small vesicles. Addition of SDS induced a transition from vesicles or threadlike micelles to spheroidal micelles. The intermediate structures, such as the appearance of small holes in the vesicle membrane, the budding of threadlike micelles from the membrane fracture, and the clusters of spheroidal micelles, were observed with increase of the SDS concentration. The electrical conductivity measurements indicated that complex micelles of SDS and silicone surfactant were formed in the solution due to the interaction between the SDS and PEO part of the silicone surfactant.     

The synthesis of a phosphadecalone system

The 2-phosphabicyclo[4.4.0]decan-5-onic system (2) was synthesized by a double Michael addition of phenylphosphine to propenylcyclohexenyl ketone (1). This dienone (1) can be prepared starting from either cyclohexanone by a known method, or from cyclohexene by its acylation with crotonic anhydride in the presence of SnCl₄. The NMR of the phosphine and several of its derivatives in comparison with the aza analog, as well as the Mass spectra fragmentation pattern, are discussed,     

Atrazine degradation by Pseudomonas strain ADP entrapped in sol-gel glass

Sol-gel entrapment was evaluated as a method for immobilization of an atrazine degrading Pseudomonas. It was found that the bacterium lost much of its atrazine degrading activity upon immobilization. However, partial activity could have been restored by amendment of nutrients. Bacteria immobilized using a prehydrolysis technique for the preparation of the sol-gel, retained better activity in comparison to bacteria immobilized using a composite calcium alginate/sol-gel procedure. Further study is underway to improve the activity of sol-gel entrapped bacteria.     

Characterization of the stereochemical selectivity of beta-hairpin formation by molecular dynamics simulations

The stability of secondary structure motifs found in proteins is influenced by the choice of the configuration of the chiral centers present in the amino acid residues (i.e., D vs L). Experimental studies showed that the structural properties of the tetrapeptide (L)V(L)P(L)A(L)L (all-L) are drastically altered upon mutating the L-proline and the L-alanine by their d-enantiomers [J. Am. Chem. Soc. 1996, 118, 6975]. The all-L diastereomer is unstructured, experiencing little or no beta-hairpin formation, while the (L)V(D)P(D)A(L)L peptide exhibits a substantial population of beta-hairpin conformation. In this study, we perform molecular dynamics simulations to investigate the folding propensity of these two model peptides. The results confirm the experimental findings, namely, that the presence of d-amino acids in the loop region strongly induces beta-hairpin formation (a population increase from about 1.5% to 50% is observed). The major factor determining the different behavior is found to be the large difference in energy between the two diastereomers, approximately 22 kJ/mol, when they adopt a beta-hairpin structure. The higher energy observed for the all-L peptide is a consequence of none-ideal hydrogen bond formation and of steric repulsions. The results suggest that selective incorporation of D-amino acids in proteins can be used to enhance certain secondary structure elements. The kinetic behavior of the folding process observed in the simulations is also investigated. We find that the decay rate of the folded structure fits to a biexponential function, suggesting that the folding/unfolding process of a beta-hairpin is governed by two different mechanisms.     

A predictive pattern of computed barriers for C-h hydroxylation by compound I of cytochrome p450

The communication presents DFT calculations of 10 different C-H hydroxylation barriers by the active species of the enzyme cytochrome P450. The work demonstrates the existence of an excellent barrier-bond energy correlation. The so-obtained equation of the straight line is demonstrated to be useful for predicting barriers of related C-H activation processes, as well as for assessing barrier heights within the protein environment. This facility is demonstrated be estimating the barrier of camphor hydroxylation by P450cam.     

Tactical store delivery planning

We describe a system for tactical planning of store deliveries that has been developed for a major US retailer. The retailer operates several distribution centres (DCs) and has over one thousand stores. The system is used for planning weekly fixed truck routes for store deliveries at minimal cost, where each route visits several stores, taking into account tight daily workload constraints in the DCs, limited daily transportation capacity, and store requirements. Initial results show a saving potential of 1–5%, amounting to several million US dollars annually, and truncation of the planning process from weeks to hours.     

Detection and Identification of Alkylating Agents by Using a Bioinspired “Chemical Nose”

Alkylating agents are simple and reactive molecules that are commonly used in many and diverse fields such as organic synthesis, medicine, and agriculture. Some highly reactive alkylating species are also being used as blister chemical‐warfare agents. The detection and identification of alkylating agents is not a trivial issue because of their high reactivity and simple structure. Herein, we report on a new multispot luminescence‐based approach to the detection and identification of alkylating agents. In order to demonstrate the potential of the approach, seven π‐conjugated oligomers and polymers bearing nucleophilic pyridine groups, 1 – 7 , were adsorbed onto a solid support and exposed to vapors of alkylators 8 – 15 . The alkylation‐induced color‐shift patterns of the seven‐spot array allow clear discrimination of the different alkylators. The spots are sensitive to minute concentrations of alkylators and, because the detection is based on the formation of new covalent bonds, these spots saturate at about 50 ppb.     

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