(3R,3′R)-astaxanthin from the yeast Phaffia rhodozyma

Astaxanthin isolated from the yeast Phaffia rhodozyma has the 3R,3′R-configuration, opposite to that of astaxanthin from other sources which have been so far investigated. This is the first example of a naturally occurring carotenoid biosynthesized in different optical forms. A possible explanation is advanced.     

MicroRNA MiR-214 Regulates Ovarian Cancer Cell Stemness by Targeting p53/Nanog

Previous studies have shown aberrant expression of miR-214 in human malignancy. Elevated miR-214 is associated with chemoresistance and metastasis. In this study, we identified miR-214 regulation of ovarian cancer stem cell (OCSC) properties by targeting p53/Nanog axis. Enforcing expression of miR-214 increases, whereas knockdown of miR-214 decreases, OCSC population and self-renewal as well as the Nanog level preferentially in wild-type p53 cell lines. Furthermore, we found that p53 is directly repressed by miR-214 and that miR-214 regulates Nanog through p53. Expression of p53 abrogated miR-214-induced OCSC properties. These data suggest the critical role of miR-214 in OCSC via regulation of the p53-Nanog axis and miR-214 as a therapeutic target for ovarian cancer.     

Stereochemical and structural effects of (2R,6R)-hydroxynorketamine on the mitochondrial metabolome in PC-12 cells

Background

Impairment in mitochondrial biogenesis and function plays a key role in depression and anxiety, both of which being associated with changes in fatty acid and phospholipid metabolism. The antidepressant effects of (R,S)-ketamine have been linked to its conversion into (2S,6S;2R,6R)-hydroxynorketamine (HNK); however, the connection between structure and stereochemistry of ketamine and HNK in the mitochondrial homeostatic response has not yet been fully elucidated at a metabolic level.

Weak absolute helicity direction in Ni-salen by trans-cyclohexane-(1R,2R)-diamine

Helical Ni-salen foldamers were synthesized from enantiomerically pure cyclohexane-(1R,2R)-diamine, N,N′-bis-(N-phenyl (4-diphenylphosphine)-3-salicylidenato carboxamide)-(1R,2R)-cyclohexanediaminato-nickel(II). X-ray structural characterization of the absolute helicities observed confirms our earlier assertions, based on solution spectroscopic evidence, that trans-cyclohexane-diamine, a common component of chiral salen catalysts, is a weak director of absolute helicity for Ni-salen.     

Complexes containing the (R,R)-N,N-bis(2-hydroxy-3-functionalised-benzylidene)-1,2-diaminocyclohexane ligand: synthesis and X-ray analyses of titanium chloro and oxo derivatives

Titanium complexes based on the (R,R)-N,N^′-bis(2-hydroxy-3-functionalised-benzylidene)-1,2-diaminocyclohexane ligand and containing either chloro or bridged oxo co-ligands have been prepared, subjected to single crystal X-ray analysis and examined as pre-catalysts for the asymmetric phospho-aldol (PA) reaction. Catalysis does take place although at a much slower rate than with related aluminium complexes and then only to afford racemic products; significant observations that lead to an important design point in PA pre-catalysts.     

Oligo-(R)-3-hydroxybutyrate modification of sorting signal enables pore formation by Escherichia coli OmpA

The outer membrane protein A (OmpA) of Escherichia coli is a well-known model for protein targeting and protein folding. Wild-type OmpA, isolated either from cytoplasmic inclusion bodies or from outer membranes, forms narrow pores of ∼ 80 pS in planar lipid bilayers at room temperature. The pores are well structured with narrow conductance range when OmpA is isolated using lithium dodecyl sulfate (LDS) or RapiGest surfactant but display irregular conductance when OmpA is isolated with urea or guanidine hydrochloride. Previous studies have shown that serine residues S163 and S167 of the sorting signal of OmpA (residues 163-169), i.e., the essential sequence for outer membrane incorporation, are covalently modified by oligomers of (R)-3-hydroxybutyrate (cOHB). Here we find that single-mutants S163 and S167 of OmpA, which still contain cOHB on one serine of the sorting signal, form narrow pores in planar lipid bilayers at room temperature with lower and more irregular conductance than wild-type OmpA, whereas double mutants S163:S167 and S163:V166 of OmpA, with no cOHB on the sorting signal, are unable to form stable pores in planar lipid bilayers. Our results indicate that modification of serines in the sorting signal of OmpA by cOHB in the cytoplasm enables OmpA to incorporate into lipid bilayers at room temperature as a narrow pore. They further suggest that cOHB modification may be an important factor in protein targeting and protein folding.     

Structure of the O-polysaccharide from the lipopolysaccharide of Providencia alcalifaciens O31 containing an ether of d-mannose with (2R,4R)-2,4-dihydroxypentanoic acid

Recently, ether-linked diastereomeric 2,4-dihydroxypentanoic acids have been reported as new components of bacterial glycans [Shashkov, A. S. et al.Nat. Prod. Commun.2008, 3, 1625-1630]. In this work, an ether of (2R,4R)-2,4-dihydroxypentanoic acid (Dhpa) with d-mannose was identified in the O-polysaccharide of Providencia alcalifaciens O31, and the polysaccharide structure was elucidated. Studies by NMR spectroscopy confirmed the ether linkage between O-2 of Dhpa and O-4 of Man, and the absolute configuration of Man was determined after ether cleavage with boron trichloride. In the polysaccharide, Dhpa was found to exist partially in the form of 1,4-lactone. Using sugar and methylation analyses along with ¹H and ¹³C NMR spectroscopy, including 2D ¹H,¹H COSY, TOCSY, ROESY, H-detected ¹H,¹³C HSQC, and gHMBC experiments, the following structure of the tetrasaccharide repeating unit of the polysaccharide was established:     

Identification and characterization of salt-responsive microRNAs in Populus tomentosa by high-throughput sequencing

Salt is one of the main environmental factors limiting plant growth and a better understanding of mechanisms of salt stress would aid efforts to bolster plant salt tolerance. MicroRNAs are well known for their important regulatory roles in response to abiotic stress in plants. In this study, high-throughput sequencing was employed to identify miRNAs in Populus tomentosa plantlets treated or not with salt (200 mM for 10 h). We found 141 conserved miRNAs belonging to 31 families, 29 non-conserved but previously-known miRNAs belonging to 26 families, and 17 novel miRNAs. Under salt stress, 19 miRNAs belonging to seven conserved miRNA families were significantly downregulated, and two miRNAs belonging to two conserved miRNA families were upregulated. Of seven non-conserved miRNAs with significantly altered expression, five were downregulated and two were upregulated. Furthermore, eight miRNAs were validated by qRT-PCR and their dynamic differential expressions were analyzed. In addition, 269 target genes of identified miRNAs were predicted and categorized by function. These results provide new insights into salt-responsive miRNAs in Populus.     

MicroRNAs target gene and signaling pathway by bioinformatics analysis in the cardiac hypertrophy

Cardiac hypertrophy is a physiological adaptive response of the heart to diverse pathophysiological stimuli. Initially, it may be adaptive to normalize wall stress and to preserve contractile performance. This adaptive process may gradually progress to dilated cardiomyopathy, fibrotic diseases, arrhythmia, heart failure and even sudden death. Although various molecular pathways responsible for the coordinated control of the hypertrophic program, little is known about their underlying molecular mechanisms. Very recently, increasing evidence showed that miRNAs are key modulators of both cardiovascular development and function, which govern the process of cardiac hypertrophy and heart failure. MicroRNAs (miRNAs) act in a complex functional network in which each single miRNAs might control thousands of distinct target genes, and each single protein-coding gene can be regulated by many different miRNAs. Identifying the roles of miRNAs, their target genes and signaling pathways in cardiac hypertrophy by bioinformatic analysis will provide more insight into the molecular mechanisms underlying this disease process. Currently, bioinformatics resource such as GO and KEGG was applied to describe the miRNAs target genes function and identify the mRNA interaction networks that are responsible for various cellular processes. It provides a useful approach to observe the function of microRNA in physiological and pathological conditions. In this review, we will give a discussion on the dysregulation of specific miRNAs in cardiac hypertrophy and signaling pathways linking the hypertrophy-regulating miRNAs to the pathological process of cardiac hypertrophy. Finally, we place special emphasis on the essential role of bioinformatics analysis to predict the target genes and miRNAs gene networks.     

VCAM-1 directed immunoliposomes selectively target tumor vasculature in vivo

Targeting the tumor vasculature and selectively modifying endothelial functions is an attractive anti-tumor strategy. We prepared polyethyleneglycol modified immunoliposomes (IL) directed against vascular cell adhesion molecule 1 (VCAM-1), a surface receptor over-expressed on tumor vessels, and investigated the liposomal targetability in vitro and in vivo. In vitro, anti-VCAM-1 liposomes displayed specific binding to activated endothelial cells under static conditions, as well as under simulated blood flow conditions. The in vivo targeting of IL was analysed in mice bearing human Colo 677 tumor xenografts 30 min and 24 h post i.v. injection. Whereas biodistribution studies using [³H]-labelled liposomes displayed only marginal higher tumor accumulation of VCAM-1 targeted versus unspecific ILs, fluorescence microscopy evaluation revealed that their localisations within tumors differed strongly. VCAM-1 targeted ILs accumulated in tumor vessels with increasing intensities from 30 min to 24 h, while control ILs accumulated in the tumor tissue by passive diffusion. ILs that accumulated in non-affected organs, mainly liver and spleen, primarily co-localised with macrophages. This is the first morphological evidence for selective in vivo targeting of tumor vessels using ILs. VCAM-directed ILs are candidate drug delivery systems for therapeutic anti-cancer approaches designed to alter endothelial function.     

The Intermediate Filament Vimentin Mediates MicroRNA miR-378 Function in Cellular Self-renewal by Regulating the Expression of the Sox2 Transcription Factor

MicroRNAs are short noncoding RNAs that are implicated in cell self- renewal and cancer development. We show that miR-378 is up-regulated in human cancers and found that tumor cells transfected with miR-378 acquired properties of tumor stem cells, including cell self-renewal. Overexpression of miR-378 enhanced cell survival and colony formation. Isolated from a single-cell colony, the miR-378-expressing cells formed tumors in nude mice at low cell densities. These cells expressed higher levels of miR-378 and formed more and larger spheres and colonies. We found that the miR-378-expressing cells contained a large number of side population cells and could undergo differentiation. Cells transfected with miR-378 expressed increased levels of Sox2. Expression of miR-378 and Sox2 was found correlated significantly in cancer cell lines and in cancer patient specimens. We also observed opposite levels of vimentin in the cancer cell lines and human breast carcinoma specimens. We further demonstrated that vimentin is a target of miR-378, and ectopic transfection of vimentin inhibited Sox2 expression, resulting in decreased cell survival. Silencing vimentin promoted Sox2 expression and cell survival. Our study demonstrates that miR-378 is a regulator of stem cell marker Sox2 by targeting vimentin, which may serve as a new tool in studying the role of stem cells in tumorigenesis.     

In silico optimization and low structured kinetic model of poly[(R)-3-hydroxybutyrate] synthesis by Cupriavidus necator DSM 545 by fed-batch cultivation on glycerol

Glycerol was utilized by Cupriavidus necator DSM 545 for production of poly-3-hydroxybutyrate (PHB) in fed-batch fermentation. Maximal specific growth rates (0.12 and 0.3 h⁻¹) and maximal specific non-growth PHB production rate (0.16 g g⁻¹ h⁻¹) were determined from two experiments (inocula from exponential and stationary phase). Saturation constants for nitrogen (0.107 and 0.016 g L⁻¹), glycerol (0.05 g L⁻¹), non-growth related PHB synthesis (0.011 g L⁻¹) and nitrogen/PHB related inhibition constant (0.405 g L⁻¹), were estimated. Five relations for specific growth rate were tested using mathematical models. In silico performed optimization procedures (varied glycerol/nitrogen ratio and feeding) has resulted in a PHB content of 70.9%, shorter cultivation time (23 h) and better PHB yield (0.347 g g⁻¹). Initial concentration of biomass 16.8 g L⁻¹ and glycerol concentration in broth between 3 and 5 g L⁻¹ were decisive factors for increasing of productivity.     

High-performance liquid chromatography separation of the (S,S)- and (R,S)-forms of S-adenosyl-l-methionine

S-adenosyl-l-methionine (AdoMet), an important biological cofactor, exists in two chiral forms, (S,S)- and (R,S)-, only the former of which is biologically active. Here, we have developed a chromatographic method to obtain pure (S,S)-AdoMet using a single C18 column.