Characteristic alkaline catalyzed degradation of kotalanol, a potent α-glucosidase inhibitor isolated from Ayurvedic traditional medicine Salacia reticulata, leading to anhydroheptitols: another structural proof

Stereochemical structure of kotalanol (2), a highly potent α-glucosidase inhibitor isolated from an Ayurvedic traditional medicine Salacia reticulata, was proved by alkaline catalyzed degradation of natural kotalanol (2), in which characteristic stereospecific cyclization of the degradative side chain leading to anhydroheptitols (10 and 11) was involved.     

Scavenging effects of metal complexes of water-soluble thiacalix[4]arenetetrasulfonate on superoxide anion radicals

The scavenging effects of metal complexes of thiacalix[4]arenetetrasulfonate (Me-TCAS[4], Me=H?, Fe3(+), Mn3(+), Mn2(+), Cu2(+), and Zn2(+)) on superoxide anion radicals (O??) generated from the xanthine-xanthine oxidase system were investigated by the nitroblue tetrazolium (NBT) method and electron spin resonance (ESR) spin-trapping method using 5,5-dimethyl-1-pyrroline-N-oxide as a trapping reagent. As a reference, calix[4]arenetetrasulfonate (H?)-CAS[4]), calix[6]arenehexasulfonate (H?-CAS[6]) and calix[8]areneoctasulfonate (H?-CAS[8]) were also examined. The results by the NBT method indicated that Fe3(+)- and Mn3(+)-TCAS[4] exhibited the highest O?? scavenging activity among Me-TCAS[4] and H?-CAS[n] (n = 4, 6, 8) in this study. The IC?? values of Fe3(+)- and Mn3(+)-TCAS[4] for O?? scavenging activity were estimated to be 5.3 and 7.8 μM, respectively, and were almost the same as those of tannin acid, catechin and their derivatives, which are known as very effective scavengers of O??. Scavenging activities were in the order of Fe3(+)- and Mn3(+)-TCAS[4]>Mn2(+)-, Cu2(+)-, and Zn(2+)-TCAS[4]>H(2)-TCAS[4] and H?-CAS[n] (n=4, 6, 8). Each activity of Me-TCAS[4] (Me=Fe3(+), Mn3(+), Mn2(+), Cu2(+), and Zn2(+)) was higher than that of the corresponding metal ion, indicating that H?-TCAS[4] has the ability to raise the activity of the metal ion itself by forming a complex. Also, the ESR spin-trapping method revealed that Fe3(+)- and Mn3(+)-TCAS[4] showed high O?? scavenging activities, similarly to the results by the NBT method.     

Synthesis of the common FGHI-ring part of ciguatoxins

The common FGHI-ring part (2) of ciguatoxins has been synthesized from the F- and I-ring parts (6 and 5, respectively). The Nozaki-Hiyama-Kishi coupling of 6 with 5 followed by regio- and stereoselective epoxidation at C29 and C30 afforded an epoxide (4), which was transformed into a tricyclic compound (3) corresponding to the F-HI-ring part by 6-exo-epoxide opening and the subsequent inversion of the C29 stereocenter. Reductive cyclization of 3 forming the C31-O26 bond of the G-ring successfully produced 2.     

Self-assembly of the light-harvesting complex of photosystem II (LHCII) on alkanethiol-modified gold electrodes

A light-harvesting complex of photosystem II (LHCII), isolated from spinach, was immobilized onto a gold electrode modified with self-assembled monolayers (SAMs) of alkanethiols, NH₂–(CH₂) _n –SH, n = 2, 6, 8, 11; HOOC–(CH₂)₇–SH; and CH₃–(CH₂)₇–SH; and a bare electrode. The extent of LHCII complex adsorption according to surface treatment decreased in the order amino groups > carboxylic acid groups > methyl groups and increased with the methylene chain length in NH₂–(CH₂) _n –SH. Interestingly, the photocurrent density depended on the terminal group and the methylene chain length in NH₂–(CH₂) _n –SH and decreased in the order amino groups > methyl groups > carboxylic acid groups. An efficient photocurrent response of the LHCII complex on SAMs of NH₂–(CH₂) _n –SH, n = 8 was observed upon illumination at 680 nm. These results indicated that the LHCII complexes were well organized on the cationic surfaces of the gold electrodes modified with amino alkanethiols. The quantum yield depended on the methylene chain length (n), where the maximum photocurrent response was observed at n = 8, which corresponded to a distance of 1.7 nm between the terminal amino group in NH₂–(CH₂)₈–SH and the gold surface.     

Phosphorothioate Modification of mRNA Accelerates the Rate of Translation Initiation to Provide More Efficient Protein Synthesis

Messenger RNAs (mRNAs) with phosphorothioate modification (PS‐mRNA) to the phosphate site of A, G, C, and U with all 16 possible combinations were prepared, and the translation reaction was evaluated using an E. coli cell‐free translation system. Protein synthesis from PS‐mRNA increased in 12 of 15 patterns when compared with that of unmodified mRNA. The protein yield increased 22‐fold when the phosphorothioate modification at A/C sites was introduced into the region from the 5′‐end to the initiation codon. Single‐turnover analysis of PS‐mRNA translation showed that phosphorothioate modification increases the number of translating ribosomes, thus suggesting that the rate of translation initiation (rate of ribosome complex formation) is positively affected by the modification. The method provides a new strategy for improving translation by using non‐natural mRNA.     

Large Amplitude Motion in 9-Methylanthracene: High-Resolution Spectroscopy and Ab Initio Theoretical Calculation

CH\begin{document}$_3$\end{document} internal rotation is one of the typical large amplitude motions in polyatomic molecules, the spectral analysis and theoretical calculations of which, were developed by Li-Hong Xu and Jon Hougen. We observed a Doppler-free high-resolution and high-precision spectrum of 9-methylanthracene (9MA) by using the collimated supersonic jet and optical frequency comb techniques. The potential energy curve of CH\begin{document}$_3$\end{document} internal rotation is expressed by a six-fold symmetric sinusoidal function. It was previously shown that the barrier height (\begin{document}$V_6$\end{document}) of 9MA-\begin{document}$d_{12}$\end{document} was considerably smaller than that of 9MA-\begin{document}$h_{12}$\end{document} [M. Baba, et al., J. Phys. Chem. A 113 , 2366 (2009)]. We performed ab initio theoretical calculations of the multi-component molecular orbital method. The barrier reduction by deuterium substitution was partly attributed to the difference between the wave functions of H and D atomic nuclei.     

Calculating a minimal sphere containing a polytope defined by a system of linear inequalities

We will propose an algorithm for calculating a minimal sphere containing a polytope defined by a system of linear inequalities in low dimensional Euclidean space. This algorithm is a straightforward application of the algorithm for maximizing a convex quadratic function over a polytope. It will be shown that this algorithm successfully generates a minimal sphere when the dimensions of the underlying space is up to five.International Digital Communication Inc.     

Tandem Time-of-Flight Mass Spectrometer with High Precursor Ion Selectivity Employing Spiral Ion Trajectory and Improved Offset Parabolic Reflectron

In this study, we have developed a tandem time-of-flight mass spectrometry (TOF/TOF) technique involving the use of a matrix-assisted laser desorption/ionization ion source that exhibits high precursor ion selectivity. An ion optical system with a 17 m spiral ion trajectory was used in the first time-of-flight mass spectrometer. High precursor ion selectivity was achieved by realizing a 15 m flight path, which is considerably longer than that of the conventional MALDI-TOF/TOF before the precursor ion selection by an ion gate; monoisotopic ions could be selected properly up to m/z 2500. Furthermore, the first time-of-flight mass spectrometer was composed of electrostatic sectors and could eliminate post-source decay (PSD) ions. Precursor ions with 20 keV kinetic energy were selected and injected into a collision cell, leading to the generation of fragment ions by high-energy collision-induced dissociation (HE-CID). The optimized second time-of-flight mass spectrometer included a post-acceleration region and an offset parabolic reflectron to record product ion spectra in the entire mass range. Our system could generate a simple HE-CID product ion spectrum because each fragment pathway could be observed as a single peak by the selection of monoisotopic ions of all precursor ions and HE-CID fragment pathways could be predominantly observed by the PSD ion elimination.     

Keeping an eye on myocilin: a complex molecule associated with primary open-angle glaucoma susceptibility

MYOC encodes a secretary glycoprotein of 504 amino acids named myocilin. MYOC is the first gene to be linked to juvenile open-angle glaucoma (JOAG) and some forms of adult-onset primary open-angle glaucoma (POAG). The gene was identified as an up-regulated molecule in cultured trabecular meshwork (TM) cells after treatment with dexamethasone and was originally referred to as trabecular meshwork-inducible glucocorticoid response (TIGR). Elevated intraocular pressure (IOP), due to decreased aqueous outflow, is the strongest known risk factor for POAG. Increasing evidence showed that the modulation of the wild-type (wt) myocilin protein expression is not causative of glaucoma while some misfolded and self-assembly aggregates of mutated myocilin may be associated with POAG in related or unrelated populations. The etiology of the disease remains unclear. Consequently, a better understanding of the molecular mechanisms underlying POAG is required to obtain early diagnosis, avoid potential disease progression, and develop new therapeutic strategies. In the present study, we review and discuss the most relevant studies regarding structural characterizations, expressions, molecular interactions, putative functions of MYOC gene and/or its corresponding protein in POAG etiology.