Diastereo‐ and Enantioselective Synthesis of Organometallic Bis(helicene)s by a Combination of C?H Activation and Dynamic Isomerization

Homochiral and heterochiral cis‐bis‐cycloplatinated‐[6]helicene derivatives 1 b^{1, 2} , as representative examples of platina[6]helicenes that share a common platinum center, have been prepared. A diastereo‐ and enantioselective synthesis, which combines CH activation and dynamic isomerization from heterochiral structure 1 b² into homochiral structure 1 b¹ , is also described. Overall, this isomerization process results in the transfer of chiral information from one helicene moiety to the other one. The chiroptical properties of homochiral (P)‐ and (M)‐ 1 b¹ were greatly modified upon oxidation into their corresponding (P)‐ and (M)‐diiodo‐Pt^IV complexes ( 5 ). The changes were also analyzed by performing theoretical calculations. C? H activation in the synthesis of organometallic helicenes is further demonstrated by the preparation of cis‐bis‐cycloplatinated‐[8]helicene 1 c .     

The influence of the shape of Au nanoparticles on the catalytic current of fructose dehydrogenase

Graphite electrodes were modified with triangular (AuNTrs) or spherical (AuNPs) nanoparticles and further modified with fructose dehydrogenase (FDH). The present study reports the effect of the shape of these nanoparticles (NPs) on the catalytic current of immobilized FDH pointing out the different contributions on the mass transfer–limited and kinetically limited currents. The influence of the shape of the NPs on the mass transfer–limited and the kinetically limited current has been proved by using two different methods: a rotating disk electrode (RDE) and an electrode mounted in a wall jet flow-through electrochemical cell attached to a flow system. The advantages of using the wall jet flow system compared with the RDE system for kinetic investigations are as follows: no need to account for substrate consumption, especially in the case of desorption of enzyme, and studies of product-inhibited enzymes. The comparison reveals that virtually identical results can be obtained using either of the two techniques. The heterogeneous electron transfer (ET) rate constants (k_S) were found to be 3.8 ± 0.3 s⁻¹ and 0.9 ± 0.1 s⁻¹, for triangular and spherical NPs, respectively. The improvement observed for the electrode modified with AuNTrs suggests a more effective enzyme-NP interaction, which can allocate a higher number of enzyme molecules on the electrode surface.

The shape of gold nanoparticles has a crucial effect on the catalytic current related to the oxidation of D-(-)-fructose to 5-keto-D-(-)-fructose occurring at the FDH-modified electrode surface. In particular, AuNTrs have a higher effect compared with the spherical one.

     

Automation of dimethylation after guanidination labeling chemistry and its compatibility with common buffers and surfactants for mass spectrometry-based shotgun quantitative proteome analysis

Isotope labeling liquid chromatography–mass spectrometry (LC–MS) is a major analytical platform for quantitative proteome analysis. Incorporation of isotopes used to distinguish samples plays a critical role in the success of this strategy. In this work, we optimized and automated a chemical derivatization protocol (dimethylation after guanidination, 2MEGA) to increase the labeling reproducibility and reduce human intervention. We also evaluated the reagent compatibility of this protocol to handle biological samples in different types of buffers and surfactants. A commercially available liquid handler was used for reagent dispensation to minimize analyst intervention and at least twenty protein digest samples could be prepared in a single run. Different front-end sample preparation methods for protein solubilization (SDS, urea, Rapigest™, and ProteaseMAX™) and two commercially available cell lysis buffers were evaluated for compatibility with the automated protocol. It was found that better than 94% desired labeling could be obtained in all conditions studied except urea, where the rate was reduced to about 92% due to carbamylation on the peptide amines. This work illustrates the automated 2MEGA labeling process can be used to handle a wide range of protein samples containing various reagents that are often encountered in protein sample preparation for quantitative proteome analysis.     

Micelles of SDS Surfactants in Concentrated NaCl Solutions

We investigated the aggregation behavior of rod-like micelles of sodium dodecyl sulfate (SDS) in concentrated NaCl solution by quasi-elastic light scattering (QLS) and viscosity measurement over a range of temperature (25 °C to 50 °C) and NaCl concentration. The reduced viscosity of aqueous SDS in the presence of NaCl has been measured by an Ubbelohde-type capillary viscometer. We show mean hydrodynamic radius of micelles can be determined from viscosity data. We also determined mean hydrodynamic radius using quasi-elastic light scattering. Micellar size decreases with increasing temperature, whereas it increases with increasing ionic strength. The results of viscosity and dynamic light-scattering measurements are interpreted as the extension of length of rod-like micelles. We compare viscosity and light scattering experimental results.     

重金属的生物吸附机理及吸附平衡模式研究*

各种生物吸附剂包括海洋微生物、发酵工业的菌丝体废渣及活性污泥的提取物等对金属离子的吸附特性已被广泛研究,本文就生物体对金属离子的吸附机理及吸附平衡模式研究进行了综述,阐明了今后的研究方向。     

Halogenation of 2-Hydroxynicotinic Acid

A convenient method to prepare 5-halo-2-hydroxy-nicotinic acid is described.     

Effects of fatty acids on growth and poly-3-hydroxybutyrate production in bacteria

The effects of saturated and unsaturated fatty acids (lauric acid, palmitic acid, steric acid, oleic acid, linoleic acid, soybean oil) on Sphaerotilus natans, 0B17 (Pseudomonas sp.), and recombinant Escherichia coli DH5(/pUC19/CAB were studied. Oleic acid enhances Poly-3-hydroxybutyrate (PHB) production in these three bacterial strains, suggesting that the single double bond of the acid activates the polyhydroxylkanoate accumulation enzymatic reaction. Under the effect of lauric acid and linoleic acid, the growth of S. natans and 0B17 were totally inhibited. However, the enhanced PHB accumulation in recombinant E. coli was observed.     

Construction of recombinant Escherichia coli strais for production of poly-(3-hydroxybutyrate-co-3-hydroxyvalerate)

Plastic wastes constitute a worldwide environmental problem, and the demand for biodegradable plastics has become high. One of the most important characteristics of microbial polyesters is that they are thermoplastic with environmentally degradable properties. In this study, pUC 19/PHA was cloned and transformed into three different Escherichia coli strains. Among the three strains that were successfully expressed in the production of polyhydroxyalkanoates (PHA), E. coli HMS174 had the highest yield in the production of poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) (P[HB-HV]). The cell dry weight and PHA content of recombinant HMS174 reached as high as 10.27 g/L and 43% (w/w), respectively, in fed-batch fermentor culture. The copolymer of PHA, P(HB-HV), was found in the cells, and the biopolymers accumulated were identified and analyzed by gas chromatography, proton nuclear magnetic resonance spectroscopy, and differential scanning calorimetry. We demonstrated clearly that the E. coli host for PHA production has to be carefully selected to obtain a high yield. The results obtained indicated that a superior E. coli with high PHA production can be constructed with a desirable ratio of P(HB-HV), which has potential applications in industry and medicine.     

Regioselective haloaromatization of 1,2-bis(ethynyl)benzene via halogen acids and PtCl2. Platinum-catalyzed 6-pi electrocyclization of 1,2-bis(1'-haloethenyl)benzene intermediates

[reaction: see text] Treatment of 1,2-bis(ethynyl)benzene (1) with aqueous HX (X = Br, I) in hot 3-pentanone (100-105 degrees C, 2 h) afforded 1,2-bis(1'-haloethenyl)benzene species 2-Br and 2-I in 98% and 95% yields, respectively. The hydrochlorination of endiyne 1 failed to proceed at elevated temperature but was implemented efficiently by PtCl2 (5 mol %) in hot 3-pentanone (100 degrees C, 2 h) to give 1,2-bis(1'-chloroethenyl)benzene 2-Cl in 80% yield. In the presence of PtCl2 (5 mol %), these halides 2-Cl,2-Br, and 2-I were subsequently converted to 1-halonaphthalenes 3-Cl, 3-Br, and 3-I in the mother solution via sequential 6-pi electrocyclization and dehalogenation reactions. PtCl2 (5 mol %) also effected direct haloaromatization of endiyne 1 with HX (X = Cl, Br, I) and gave 1-halonaphthalenes 3-Cl, 3-Br, and 3-I in 64-71% yields. This investigation reports the scope and the regioselectivity of haloaromatization of various enediynes catalyzed by PtCl2.