Total synthesis of the elastin crosslinker (+)-desmopyridine

Desmopyridine, isolated from the acid hydrolysates of bovine ligamentum nuchae, is an elastin crosslinker and an amino acid that has a 3,4,5-trisubstituted pyridine skeleton. Herein we report the first total synthesis of (+)-desmopyridine in 10% yield over six steps starting from 4-aminopyridine via chemo- and regioselective palladium-catalyzed Sonogashira and Negishi cross-coupling reactions.     

Liquid structures of 1-butyl-3-methylimidazolium tetrafluoroborate and carbon dioxide mixtures by X-ray diffraction measurements

X-ray diffraction measurements for the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF₄], mixed with CO₂ were carried out at high pressures using our developed polymer cell. The intermolecular distribution functions obtained for [BMIM][BF₄]–CO₂ mixtures showed that CO₂ molecules are preferentially solvated to the [BF₄]⁻ anion. The similar preferential solvation was previously observed in analogous 1-btuyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF₆], with a different anion, which is in harmony with the present results in [BMIM][BF₄]–CO₂.     

Functional regression modeling via regularized Gaussian basis expansions

We consider the problem of constructing functional regression models for scalar responses and functional predictors, using Gaussian basis functions along with the technique of regularization. An advantage of our regularized Gaussian basis expansions to functional data analysis is that it creates a much more flexible instrument for transforming each individual’s observations into functional form. In constructing functional regression models there remains the problem of how to determine the number of basis functions and an appropriate value of a regularization parameter. We present model selection criteria for evaluating models estimated by the method of regularization in the context of functional regression models. The proposed functional regression models are applied to Canadian temperature data. Monte Carlo simulations are conducted to examine the efficiency of our modeling strategies. The simulation results show that the proposed procedure performs well especially in terms of flexibility and stable estimates.     

DNA Interaction with PtCl<Subscript>2</Subscript>(LL) (LL = Chelating Diamine Ligand: <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-Dimethyltrimethylendiamine) Complex

The [PtCl₂(LL)] complex, as a cisplatin derivative, which LL is diamine chelate ligand (N,N-dimethyltrimethylendiamine), was synthesized and characterized by elemental analysis (CHN) mass, ¹H, and ¹³C nuclear magnetic resonance techniques. Then the binding of this complex to calf thymus DNA was investigated by various physicochemical methods such as spectrophotometric, circular dichroism, spectrofluorometric, melting temperature, and viscosimetric techniques. Upon addition of the complex, important changes were observed in the characteristic UV–Vis bands (hypochromism) of calf thymus DNA, increase in melting temperature and some changes in specific viscosity. Also, the fluorescence spectral characteristics showed an increase in the fluorescence intensity of methylene blue–DNA solutions in the presence of increasing amounts of metal complex, indicating PtCl₂(LL) is able to displace the methylene blue bound to DNA but not as complete as intercalative molecules. The experimental results showed that the platinum complex is bound to DNA non-intercalatively, and an outside binding is the preferred mode of interaction.     

An efficient synthesis of 3-aryl-2-aryl(or methyl)sulfanylbenzo[b]thiophenes via cyclization of aryl 2-aryl(or methyl)sulfanylmethylsulfanylphenyl ketones

A convenient method for the preparation of 2-aryl(or methyl)sulfanylbenzo[b]thiophenes has been developed. Thus, aryl 2-aryl(or methyl)sulfanylmethylsulfanylphenyl ketones, easily prepared from readily available aryl 2-sulfanylphenyl ketones or 2-chloro-5-nitrophenyl phenyl ketone, are treated with LDA in 1,2-dimethoxyethane (DME) to give 3-aryl-2-aryl(or methyl)sulfanylmethylsulfanyl-2,3-dihydrobenzo[b]thiophen-3-ols, which in turn were dehydrated with thionyl chloride to afford 3-aryl-2-aryl(or methyl)sulfanylbenzo[b]thiophenes in reasonable overall yields.     

Bis(2-t-butylphenyl)phosphonoacetamides for the highly cis-selective synthesis of α,β-unsaturated amides

New Horner–Wadsworth–Emmons reagents, (o-t-BuPhO)₂P(O)CH₂CONMe(OMe) and (o-t-BuPhO)₂P(O)CH₂CON(CH₂CH₂) ₂O were prepared via the Arbuzov reaction in good yields. The HWE reaction of these reagents with a variety of aldehydes gave cis-α,β-unsaturated amides with high selectivity in almost quantitative yields.     

Metal‐Ion Selectivity of Chemically Modified Uracil Pairs in DNA Duplexes

DNA duplexes containing 5‐modified uracil pairs (5‐bromo, 5‐fluoro, and 5‐cyanouracil) bind selectivity to metal ions. Their selectivity is sensitive to the pH value of the solution (see picture), as the acidities of the modified uracil bases vary according to the electron‐withdrawing properties of the substituents.

     

Macromol. Biosci. 3/2009

The effect of Ph‐OH group content on gelation time, mechanical properties, hydrophobicity, and cellular adhesiveness of hydrogels produced from carboxymethylcellulose derivatives is investigated. A higher Ph‐OH group content induces faster gelation and yields more brittle and hydrophobic gels. After 4 h of seeding, a larger number of L929 fibroblasts adhere to the hydrogel of the CMC‐Ph that contains 15.4 Ph‐OH groups per 100 repeat units of uronic acid (97% adhesion rate) than to the gel of CMC‐Ph with only 8.4 Ph‐OH groups (62% adhesion rate). The results demonstrate that controlling the Ph‐OH group content is an effective and useful way to control cellular adhesion and proliferation on the hydrogels, as well as gelation time and mechanical properties of the gels.

     

Mechanism of the conformational change of the F1-ATPase β subunit revealed by free energy simulations

F(1)-ATPase is an ATP-driven rotary motor enzyme. The β subunit changes its conformation from an open to a closed form upon ATP binding. The motion in the β subunit is regarded as a major driving force for rotation of the central stalk. In this Article, we explore the conformational change of the β subunit using all-atom free energy simulations with explicit solvent and propose a detailed mechanism for the conformational change. The β subunit conformational change is accomplished roughly in two characteristic steps: changing of the hydrogen-bond network around ATP and the dynamic movement of the C-terminal domain via sliding of the B-helix. The details of the former step agree well with experimental data. In the latter step, sliding of the B-helix enhances the hydrophobic stabilization due to the exclusion of water molecules from the interface and improved packing in the hydrophobic core. This step contributes to a decrease in free energy, leading to the generation of torque in the F(1)-ATPase upon ATP binding.