Controlling orientations of immobilized oligopeptides using N-terminal cysteine labels

This letter reports a strategy of using N-terminal cysteine labels for controlling the immobilization of oligopeptides on aldehyde-terminated surfaces through the formation of stable thiazolidine rings. We also study the effect of cysteine position (either N-terminal or C-terminal) and lysine residue on the immobilization of oligopeptides. On the basis of our ellipsometry and quartz crystal microbalance (QCM) results, we conclude that the proposed immobilization strategy is highly site-specific. It works only when cysteine is in the N-terminal position, and the formation of thiazolidine is much faster than the formation of imines between lysine residues and aldehydes, even in the presence of a reducing agent such as NaBH(3)CN. By labeling an oligopeptide CSNKTRIDEANNKATKML with an N-terminal cysteine, we immobilize this oligopeptide on an aldehyde-terminated surface and investigate the enzymatic activity of trypsin acting on the oligopeptide. It is found that trypsin is able to cleave the immobilized oligopeptide having a single anchoring point at the N-terminal cysteine. No cleavage is observed when the oligopeptide is immobilized through multiple anchoring points at lysine residues.     

Adsorption of 4‐tert‐Butylpyridine on TiO2 Surface in Dye‐Sensitized Solar Cells

4‐tert‐Butylpyridine (4‐TBP) has been widely used as additive in dye‐sensitized solar cells (DSC), owing to its improvement of the fill factor and the open circuit voltage of DSC. In this paper, the adsorption of 4‐TBP on the rutile TiO₂(110) surface in DSC was studied by using the density functional theory at DFT/B3LYP level. By comparing the results with those attained from experiments, it was concluded that the 4‐TBP could chemiadsorb on the incompletely covered surface Ti atoms in the electrode. The probable mechanism of compressed recombination by coordinated 4‐TBP in DSC was proposed.     

A simple and efficient synthesis of the valsartan

Valsartan 1, one of the most important agents used in antihypertensive therapy today, was synthesized starting from L-valin methyl ester hydrochloride 2 through four steps in an overall yield of 60%. The key step involves the palladium-catalyzed Suzuki coupling. This method overcomes many of the drawbacks associated with the previously reported syntheses and is more suitable for industrial production.     

The first total synthesis of ligudentatin A

Ligudentatin A 1, a new phenolic norsesquiterpenes, was first synthesized starting from （＋）-perillaldehyde 3 through five steps, successively, in an overall yield of 20.8%. The key steps were the Diels-Alder reaction and aromatization of enone to phenol.     

Chemical inequivalence behavior of the protons attached to the same carbon in ethylene-propylene copolymer（EPC）

Six ethylene-propylene copolymer samples with different structural parameters were analyzed by ^1H NMR,^13C NMR and ^1H-^13C COSY in this paper.With the aid of the ^1H-^13C COSY spectra of ethylene-propylene copolymer,the chemical inequivalence behavior of the protons attached to the same carbon in the ethylene-propylene copolymer could be observed. Four basic types of chemical bonds were divided,and two kinds of main conformations were proposed to explain this phenomenon. Based on the calculation of conformation distribution,it can be proved that the explanation of this phenomenon was reasonable.     

First total synthesis of 10α-hydroxy-4-muurolen-3-one and its C10-isomer

An efficient synthetic route to muurolane type sesquiterpenes starting from （R）-carvone, employing allylic diazene rearrangement and the ring closing methesis （RCM） reaction as key steps, is described. The first asymmetric total synthesis of （-）-10α- hydroxy-4-muurolen-3-one 11 and （-）-10β-hydroxy-4-muurolen-3-one C was accomplished. Through the total synthesis, the absolute configurations of the natural products A, B and C were established.     

Mixed-Valence 24-Vanadophosphate Decorated with Six RuII(dmso)3 Groups: [{RuII3(dmso)9PVV11VIVRuIIIO37(OH)3}2]8?

The mixed-valence 24-vanadophosphate (1) has been synthesized and characterized in the solid state by IR, magnetism, EPR, XPS, and elemental analysis. Single-crystal X-ray analysis was carried out on (Na-1), which crystallizes in the triclinic system, space group , with a = 17.168(3) ?, b = 18.1971(14) ?, c = 20.1422(13) ?, α = 114.753(3)°, β = 99.390(4)°, γ = 95.124(4)°, and Z = 2. Polyanion 1 has an unusual, open structure composed of 2 Ru^IIIO₆ octahedra, 2 V^IVO₆ octahedra, 14 V^VO₅ square-pyramids, 8 V^VO₄ tetrahedra, and 2 PO₄ tetrahedra which are all directly linked via edges and corners. The outer surface of 1 is decorated with six Ru^II(dmso)₃ groups. XPS studies on Na-1 confirm the presence of 2 Ru^III and 6 Ru^II as well as 22 V^V and 2 V^IV centers. Magnetic susceptibility data on Na-1 show that the V^IV–Ru^III pairs are coupled antiferromagnetically, with J ₁ = −13 K and J ₂ ∼ −3 K. We did not detect any peak in our EPR measurements on Na-1, thus supporting the conclusion that Na-1 is diamagnetic in its ground state. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. In Memoriam Prof. F. A. Cotton     

A hierarchical algorithm for calculating the isotopic fine structures of molecules

This article presents a memory efficient algorithm for accurately calculating the isotopic fine structures of molecules. Treating individual isotopic species of a molecule as different mass states, we introduce the concept of transitions between mass states and represent all mass states of the molecule in a hierarchical structure. We show that there exists a simple relationship between two different mass states at two different levels of the hierarchical structure. This allows us to efficiently and accurately compute both the mass and the abundance of every mass state of a small to medium-sized molecule, whose gross structures include small number of fine structures. A truncated calculation of this algorithm can be applied to calculate a majority of isotopic species (99.99% of cumulative abundance) of a large molecule.     

Synthesis of carboxymethyl potato starch and comparison of optimal reaction conditions from different sources

Carboxymethyl potato starch (CMPS) was synthesized under heterogeneous reaction conditions. The influences of etherification temperature, alkalization and etherification time, sodium hydroxide to monochloroacetic acid (MCA) molar ratio (n_NaOH/n_MCA), theoretical degree of substitution (DS_t), the ratio of isopropyl alcohol (IPA) volume to starch mass (v_IPA/m_st) on degree of substitution (DS) and reaction efficiency (RE) of CMPS were investigated. Compared with the previous literature data, the results had significant difference for the optimal carboxymethylation conditions of potato starch from different sources. CMPS prepared under optimal conditions showed the highest DS and RE, which were 1.36 and 0.88, respectively. Furthermore, the RE value in this work is considerably higher than that reported in the literature. The time of alkalization and etherification were also discussed independently. In addition, CMPS was characterized by Fourier transform infrared spectrophotometry and scanning electron microscopy (SEM). Copyright © 2008 John Wiley & Sons, Ltd.     

Lanthanide Coordination Polymers Constructed from Infinite Rod‐Shaped Secondary Building Units and Flexible Ligands

Three lanthanide coordination polymers constructed from infinite rod‐shaped secondary building units (SBUs), [Nd₂(H₂O)₂(cis‐chdc)₂(trans‐chdc)]?2H₂O ( 1 ), Nd₂(H₂O)₄(trans‐chdc)₃ ( 2 ), and [Sm₂(H₂O)₂(cis‐chdc)(trans‐chdc)₂]?4H₂O ( 3 ) (chdcH₂=1,4‐cyclohexanedicarboxylic acid), were hydrothermally synthesized and structurally characterized. The structures of 1 – 3 are modulated by different ratios of the cis and trans configurations of chdc^2? ligands, which was achieved by temperature control in the hydrothermal reactions. Crystal‐structure analysis revealed that 1 is a four‐connected pcu‐type rod packing network built from cross‐linking of rod‐shaped neodymium–oxygen SBUs by cis‐ and trans‐chdc^2? ligands in a 2:1 ratio, 2 displays a complicated six‐connected hex‐type rod packing structure built by connection of rod‐shaped neodymium–oxygen SBUs and trans‐chdc^2? ligands, and 3 features an unprecedented five‐connected rod packing pattern constructed from rod‐shaped samarium–oxygen SBUs and cis‐ and trans‐chdc^2? ligands in a 1:2 ratio.