A strategy to enhance the binding affinity of fluorophore-aptamer pairs for RNA tagging with neomycin conjugation

Fluorogenic sulforhodamine-neomycin conjugates have been designed and synthesized for RNA tagging. Conjugates were fluorescently activated by binding to RNA aptamers and exhibited greater than 250-400 fold enhancement in binding affinity relative to corresponding unconjugated fluorophores.     

Stereoselective synthesis of novel pyrazole derivatives using tert-butansulfonamide as a chiral auxiliary

A novel chiral pyrazole derivative was developed by our research program as a potent PDE4 inhibitor for the treatment of anti-inflammatory diseases, such as asthma and chronic obstructive pulmonary disease. The asymmetric synthesis of the inhibitors carrying the pyrazole moiety, including nitrogen directly bonded to a chiral center, through a novel approach is disclosed. The key steps of the synthetic sequence begin with the preparation of chiral toluenesulfinyl imine by the condensation of (R)- and (S)-tert-butanesulfinamide with an aldehyde. Next, a corresponding chiral amine synthesis by a stereoselective addition reaction of 4-picolyl lithium to the chiral toluenesulfinyl imine is performed, followed by desulfination. The preparation of the cis-type enaminone from the addition of the enaminone to the corresponding chiral amine is then accomplished, with further transformation into the pyrazole derivatives through the amination of the enaminones and subsequent dehydro-cyclization. A total of 8 steps are completed to produce a 5.5% yield (100% ee).     

The McCoy Condition on Noncommutative Rings

We introduce the multiplication algebra of a Bernstein algebra, establish its Peirce decomposition relative to an idempotent of A and state some basic properties of this algebra of endomorphtsms     

Use of allylic strain to enforce stereochemistry. Direct syntheses of 7,8-dihydroxycalamenene and mansonone C

[Structure: see text] Direct syntheses of 7,8-dihydroxycalamenene and mansonone C were achieved. The cis-stereochemistry required for the synthesis of 7,8-dihydroxycalamenene was introduced by an intramolecular cyclization directed by allylic strain.     

Sequencing of three-component olefin metatheses: total synthesis of either (+)-gigantecin or (+)-14-deoxy-9-oxygigantecin

[Structure: see text] An efficient, flexible, and highly convergent strategy for accessing skipped bis-THF containing Annonaceous acetogenins is demonstrated by the synthesis of each of (+)-gigantecin (1) and its constitutional isomer (+)-14-deoxy-9-oxygigantecin (11). The skeleton of each compound is produced, at will, from the same precursors via a three-component ring-closing/cross-metathesis sequence that differs only in the ordering of the RCM vs CM events. Another notable aspect is the use of in situ epoxide-closing and -opening of iodohydrins with dimethylsulfonium methylide to provide inverted allylic alcohols.     

Aminolyses of 4-nitrophenyl phenyl carbonate and thionocarbonate: effect of modification of electrophilic center from C=O to C=S on reactivity and mechanism

A kinetic study is reported for nucleophilic substitution reactions of 4-nitrophenyl phenyl carbonate (5) and 4-nitrophenyl phenyl thionocarbonate (6) with a series of primary amines. The thiono compound 6 is less reactive than its oxygen analogue 5 toward strongly basic amines but is more reactive toward weakly basic CF3CH2NH2. The Br?nsted-type plots obtained from the aminolyses of 5 and 6 are curved downwardly. The reactions are proposed to proceed through a stepwise mechanism with a change in the RDS on the basis of the curved Br?nsted-type plots. The microscopic rate constants (k(1) and k(2)/k(-1) ratio) associated with the current aminolyses are consistent with the proposed reaction mechanism. The replacement of the C=O bond in 5 by a polarizable C=S group results in a decrease in the k(1) value but an increase in the k(2)/k(-1) ratio. Besides, such a modification of the electrophilic center causes a decrease in pKa degrees , defined as the pK(a) at the curvature center of curved Br?nsted-type plots, but does not alter the reaction mechanism. The larger k(2)/k(-1) ratio for the reactions of 6 compared to those of 5 is proposed to be responsible for the decreased pK(a) degrees value.     

Effect of the internal microstructure in rapid-prototyped polycaprolactone scaffolds on physical and cellular properties for bone tissue regeneration

Biomedical scaffolds should be designed to optimize their inter-microstructure to enable cell infiltration and nutrient/waste transport. To acquire these properties, several structural parameters, such as pore size, pore shape, porosity, pore interconnectivity, permeability, and tortuosity are required. In this study, we explored the effect of tortuosity on the viable cell proliferation and mineralization of osteoblast-like-cells (MG63) in polycaprolactone scaffolds. For analysis, we designed four different scaffolds of various tortuosities ranging from 1.0 to 1.3 under the same porosity (56?%) and 100?% pore interconnectivity. The pore size of the scaffolds was set as 150 and 300?μm, and a mixture of these sizes. We found that despite the porosity being same, the elastic modulus was dependent on the pore size of the scaffolds due to the distributed stress concentration. In addition, the relative water movement within scaffolds was also related to the internal microstructure. Cell viability and Ca²⁺ deposition of the cell-seeded scaffolds showed that the proliferation of viable cells and mineralization in the scaffolds with appropriate tortuosity (1.2) was relatively high compared to those of the scaffolds displaying low (1.05 and 1.1) or high (1.3) tortuosity. Our findings indicated that the internal microstructure of the scaffolds may influence not only the physical properties, but in addition the cellular behavior.