Adsorption affinity of certain biomolecules onto polymeric resins: Interpretation from molecular orbital theory

Molecular interactions have been studied for adsorption of certain biomolecules in aqueous solutions using two different types of polymeric resins as adsorbents. Molecular modeling study is based on molecular orbital theory. Adsorption affinity expresses as the slope of the linear region of the isotherm for a solute is found to be different for different adsorbents, and this difference can be interpreted from the differences in sorbent surface chemistry and morphological structure. The adsorptive interaction on the polymeric resins computed on the basis of frontier orbital theory seems to correlate well with the experimentally measured adsorption affinity. Electronic states of adsorbent and adsorbate were calculated using the semiempirical molecular orbital (MO) method from which energy of adsorption in aqueous solution was estimated. It was found that charge transfer interaction plays an important role in the adsorption of certain biomolecules on aqueous solution. The experimentally measured enthalpy of adsorption seems to correlate well with the adsorptive interaction energy computed from molecular orbital theory.     

Preparation of a novel 16-DPA-P2S5 adduct and its application as a masked α,β-unsaturated ketone in [4+2]cycloaddition reactions

The reaction of 16-DPA with P₄S₁₀ in refluxing benzene afforded a novel adduct 16-DPA-P₂S₅ instead of the expected thione. The adduct undergoes [4+2]cycloaddition with alkyne dienophiles to afford steroidal (17,16-c)pyrans.     

A validated high‑performance thin-layer chromatography method for the simultaneous determination of quercetin and gallic acid in Annona reticulata L.

JPC – Journal of Planar Chromatography – Modern TLC - A sensitive and reliable high-performance thin-layer chromatography (HPTLC) method has been developed to simultaneously estimate...     

Block copolymers based on 2‐vinyl‐4,4‐dimethyl‐5‐oxazolone by RAFT polymerization: Experimental and computational studies

The ability of 2‐vinyl‐4,4‐dimethyl‐5‐oxazolone (VDM), a highly reactive functional monomer, to produce block copolymers by reversible addition fragmentation chain transfer (RAFT) sequential polymerization with methyl acrylate (MA), styrene (S), and methyl methacrylate (MMA) was investigated using cumyl dithiobenzoate (CDB) and 2‐cyanoisopropyl dithiobenzoate (CPDB) as chain transfer agents. The results show that PS‐b‐PVDM and PMA‐b‐PVDM well‐defined block copolymers can be prepared either by polymerization of VDM from PS‐ and PMA‐macroCTAs, respectively, or polymerization of S and MA from a PVDM‐macroCTA. In contrast, PMMA‐b‐PVDM block copolymers with controlled molecular weight and low polydispersity can only be obtained by using PMMA as the macroCTA. Ab initio calculations confirm the experimental studies. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Facile synthesis of highly luminescent ZnSe(S) alloyed quantum dot for biomedical imaging

An alloyed complex of zinc, sulphur and selenium was synthesized in a controlled fashion using 3-mercaptopropionic acid (MPA) surfactant to obtain a new class of biocompatible, highly luminescent imaging probes. These ZnSe(S) alloyed quantum dots (QDs) exhibited a five fold enhancement in photoluminescence over the native ZnSe nanocrystals. The enhancement in photoluminescence was brought about without any post-preparative surface treatments, under ambient conditions. 3-mercaptopropionic acid (MPA) was found to optimally stabilize the ZnSe(S) alloyed system. The incorporation of S^2? from MPA after prolonged refluxing time enabled the formation of ZnSe(S) alloyed QDs with low cytotoxicity. The in vitro assays revealed the synergistic enhancement of photoluminescence with enhancement in dispersibility and high biocompatibility for the ZnSe(S) system. The experimental findings give us a novel range of blue-emitting, Zn-based high luminescence QDs for development of nano-probes for bioimaging applications.     

Explicit evaluations of Ramanujan-Göllnitz-Gordon continued fraction

In this paper, we establish several theorems for the explicit evaluations of Ramanujan-G?llnitz-Gordon continued fraction by using some parameterizations of Ramanujan’s theta-functions. Nayandeep Deka Baruah, Corresponding author. Research partially supported by grant SR/FTP/MA-02/2002 from DST, Govt. of India. Authors’ address: Nayandeep Deka Baruah and Nipen Saikia, Department of Mathematical Sciences, Tezpur University, Napaam-784028, Assam, India     

Diastereoselective synthesis of substituted tetrahydrothiopyrans via (3,5)-thionium-ene cyclization reaction

Tetrahydrothiopyrans have been efficiently synthesized in good yields with excellent diastereoselectivity from aldehydes and substituted 5-methylhex-4-ene-1-thiol via (3,5)-thionium-ene cyclization reaction mediated by boron trifluoride etherate.     

A comparative study of thermal decomposition behaviour of Zn-Cr,Zn-Cr-Al and Zn-Al type layered double hydroxides

Hydrolysis of ZnO in acidic pH provides a facile route for synthesis of layered double hydroxides (LDH) bearing Zn²⁺ with Cr³⁺ and Al³⁺ without having carbonate ion in the inter-layer position. The thermal decomposition of the prepared LDH show that with the increase of Cr³⁺ content in the system there is an increase in the thermal stability of the compounds. In case of Zn-Cr LDH there is a non-mass loss transition around 420°C. Segregation of parent LDH structure to a bivalent oxide and a spinel takes place in both Zn-Cr and Zn-Al LDH only at temperatures above 550°C.Authors are grateful to Director R. R. L. Jorhat for his kind permission to publish the work, as well as acknowledgement is due to Prof. Herbert Poellmann of University of Halle, Germany for some powder XRD runs. Also, acknowledgement is due to Ministry of Environment and Forests, Govt. of India for some financial assistance.     

Improved but low-x approximated relation betweenF 2 p scaling violation and gluon momentum distribution function

We present a brief analysis on the approximate methods for the determination of gluon distribution from the scaling violation of proton structureF ₂ ^p in the low-x limit. In the leading order, a general low-x approximated relation is presented having more accuracy than the previous methods. Next-to-leading order correction is presented incorporating double-log-approximation. The proposed method is found to give good agreement with data. It may also be used to discriminate between the sets of gluon distributions in the low-x.     

Effect of Association of Bromophenol Blue with Tween Surfactants on Its Acid-Base Equilibria at High pH

The acid base equilibria of the sulfonephthalein dye bromophenol blue (BPB) in aqueous nonionic micellar solutions of Tween 20, Tween 40, Tween 60, and Tween 80 have been investigated spectroscopically using a partition equilibrium method. A visible red shift in the absorbance of the basic form of the dye with increase in surfactant concentration was observed at and above pH 6.98. This has been attributed to the stabilization of the acid form of the dye by the POE groups on the head of the surfactant monomers. Such stabilization effect was found to decreases with decrease in the number of carbon atom in the hydrophobic tail and with the increase in the hydrophile-lipophile balance (HLB) of the surfactant molecule. The equilibrium constant of the partition of the dyes between micellar and aqueous pseudophases (K_ass) was found to increase with the surfactants in the order Tween 80 < Tween 60 < Tween 40 < Tween 20. The pK_a2 of the dyes were predicted and found to be in good agreement with the experimental values.