Study of interaction of proton transfer probe 1-hydroxy-2-naphthaldehyde with serum albumins: a spectroscopic study

In the present work, we have studied the interaction of proton transfer probe 1-hydroxy-2-naphthaldehyde (HN12) with Human Serum Albumin (HSA) and Bovine Serum Albumin (BSA) by steady state absorption and emission spectroscopy combined with time resolved fluorescence measurements. The measured binding constant (K) and free energy change (DeltaG) indicate a stronger affinity of HN12 molecule for HSA than BSA. Steady state anisotropy, excitation anisotropy and fluorescence resonance energy transfer (FRET) studies indicate that the probe molecule resides at the hydrophobic site of the protein environment.     

Synthesis of carbohydrate-conjugated nanoparticles and quantum dots

Nanoparticle-based probes are emerging as alternatives to molecular probes due to their various advantages, such as bright and tunable optical property, enhanced chemical and photochemical stability, and ease of introduction of multifunctionality. This work presents a simple and general approach for functionalizing various nanoparticle systems for use as glycobiological probes. Silica-coated nanoparticles of Ag, Fe3O4, and ZnS-CdSe were synthesized and functionalized with dextran. The resulting 10-40-nm-sized particles were robust, water-soluble, colloidally stable, and biochemically active.     

Electronic and infrared spectroscopy of jet-cooled (+/-)-cis-1-amino-indan-2-ol hydrates

The role of conformational isomerism in molecular interaction has been studied using the example of jet-cooled complexes of (+/-)-cis-1-amino-indan-2-ol with water. The two formerly evidenced conformers of (+/-)-cis-1-amino-indan-2-ol easily form hydrates and dihydrates, which have been studied by means of laser-induced fluorescence and IR/UV double resonance spectroscopy, as well as ab initio calculations. All the 1 : 1 and 1 : 2 complexes with water evidenced in this work involve "ring" structures, in which the water monomer or dimer acts as an acceptor from the NH(2) and a donor to the OH groups of (+/-)-cis-1-amino-indan-2-ol. However, the water lies externally to the indan frame in the hydrates of conformer I of (+/-)-cis-1-amino-indan-2-ol, which possesses axial NH(2) and equatorial OH groups, and above it for the hydrates with the less stable conformer II, with equatorial NH(2) and axial OH groups. Consequently, the different steric constraints which exist in the two conformers result in different hydrogen bond topologies, with an additional OH[dot dot dot]pi interaction for the hydrates of conformer II.     

Wetting and electrowetting properties of carbon nanotube templated parylene films

In this study, we compared the wetting and electrowetting properties of a planar parylene (poly(p-xylylene)) film to those of a nanostructured parylene film. To generate the nanostructured film, we used an aligned array of multiwalled carbon nanotubes as a template; a thin coating of parylene was deposited on the nanotube template to generate a parylene film with a nanoscale roughness structure. Static contact angle measurements indicated a very significant increase in the water contact angle from approximately 73 degrees for planar parylene to approximately 110 degrees for the nanotemplated parylene. In addition, we performed electrowetting experiments to dynamically tune the contact angle by application of electric potential. Interestingly, the flat parylene film showed contact angle saturation at an applied voltage of approximately 40 V, while the nanotemplated parylene film did not experience saturation in the contact angle response even for voltages up to 80 V. These results show that engineering a nanoscale roughness structure to a polymer film results in significant changes to the wetting and electrowetting properties of the polymer.     

Photoinduced intramolecular charge transfer reaction in (E)-3-(4-Methylamino-phenyl)-acrylic acid methyl ester: A fluorescence study in combination with TDDFT calculation

A donor-acceptor substituted aromatic system (E)-3-(4-Methylamino-phenyl)-acrylic acid methyl ester (MAPAME) has been synthesized, and its photophysical behavior obtained spectroscopically has been compared with the theoretical results. The observed dual fluorescence from MAPAME has been assigned to emission from locally excited and twisted intramolecular charge transfer states. The donor and acceptor angular dependency on the ground and excited states potential energy surfaces have been calculated both in vacuo and in acetonitrile solvent using time dependent density functional theory (TDDFT) and TDDFT polarized continuum model (TDDFT-PCM), respectively. Calculation predicts that a stabilized twisted excited state is responsible for red shifted charge transfer emission.     

On competitiveness in uniform utility allocation markets

We call a market competitive if increasing the endowment of one buyer does not increase the equilibrium utility of another. We show that every competitive uniform utility allocation market is a submodular utility allocation market, answering a question of Jain and Vazirani [K. Jain, V.V. Vazirani, Eisenberg-Gale markets: Algorithms and structural properties, in: STOC, 2007]. Our proof proceeds via characterizing non-submodular fractionally sub-additive functions.     

Synthetic applications of Baylis-Hillman chemistry: an efficient and solely stereoselective synthesis of (E)-alpha-methylcinnamic acids and potent hypolipidemic agent LK-903 from unmodified Baylis-Hillman adducts

An efficient and solely stereoselective synthesis of (E)-alpha-methylcinnamic acids has been accomplished in single pot by reduction of the unmodified Baylis-Hillman adducts, methyl-3-hydroxy-3-aryl-2-methylenepropanoates with I(2)/NaBH(4) reagent system at room temperature followed by hydrolysis. The efficacy of this method has been proved in the total synthesis of 1-[p-(myristyloxy)-alpha-methylcinnamoyl]glycerol, LK-903, a highly active hypolipidemic agent.     

Arraying of intact liposomes into chemically functionalized microwells

Here, we describe a protocol to bind individual, intact phospholipid bilayer liposomes, which are on the order of 1 microm in diameter, in microwells etched in a regular array on a silicon oxide substrate. The diameter of the wells is on the order of the liposome diameter, so only one liposome is located in each well. The background of the silicon oxide surface is functionalized with a PEG oligomer using the contact printing of a PEG silane to present a surface that resists the adsorption of proteins, lipid material, and liposomes. The interiors of the wells are functionalized with an aminosilane to facilitate the conjugation of biotin, which is then bound to Neutravidin. The avidin-coated well interiors bind the liposomes whose surfaces contain biotinylated lipids. The specific binding of the liposomes to the surface using the biotin-avidin linkage, together with the resistant nature of the background and the physical confinement of the wells, allows the liposomes to remain intact and to not unravel, rupture, and fuse onto the surface. We demonstrate this intact arraying using confocal laser scanning microscopy of fluorophores specifically tagging the microwells, the lipid bilayer, and the aqueous interior of the liposome.     

Construction of an inexpensive surface plasmon resonance instrument for use in teaching and research

The construction of an inexpensive SPR instrument that can be used for both teaching and research is described. Using a 2′ × 2′ optical table to construct this instrument allows both scientists and students full access to the operation of the spectrometer. Furthermore, the use of open platform instrumentation has the advantage of maintaining the focus on the relationship between emerging technology and analytical chemistry as well as allowing the user to modify the instrument to enhance the measurement process for a particular application. This is a change from the learning paradigm used in most research and teaching laboratories where commercial instrumentation is treated as a black box due to its complexity. Three studies, which were performed using this instrument, are presented to demonstrate the suitability of this instrument for both teaching and research. These studies include measuring the refractive index of alcohols, investigating the partitioning of ruthenium (II) trisbipyridine chloride into Nafion, and understanding the mechanism controlling metal ion adsorption by polyacrylamide hydrogels.