Naked eye detection of nitric oxide release from nitrosothiols aided by gold nanoparticles

In this work we have demonstrated that nitric oxide can be monitored spectrophotometrically using cyclodextrin encapsulated ferrocene. The detection course showed the colour change from yellow to blue which can be detected with the naked eye. Also we describe the catalytic effect of gold nanoparticles in enhancing nitric oxide release from S-nitrosothiols.     

Helical folding in heterogeneous foldamers without inter-residual backbone hydrogen-bonding

This communication describes a set of hybrid foldamers that do not feature inter-residual, but intra-residual backbone hydrogen-bonding, yet adopt a preferentially folded conformation displaying right-handed helical architecture. Conformational ordering is apparently due to the combined conformational restrictions imposed by the conformationally restricted individual amino acid residues with which the oligomers are made of.     

Thermal analysis of water and magnesium hydroxide content in commercial pharmaceutical suspensions milk of magnesia

A standard protocol was developed to determine the water content by thermal analysis of milk of magnesia (MoM). Differential scanning calorimetry (DSC) and thermogravimetry (TG) were used in a novel manner for examining the physical characteristics of the commercial pharmaceutical suspensions. Moisture analyzer and oven-dry methods validate the proposed protocol. MoM consists primarily of water and magnesium hydroxide [Mg(OH)₂]. Experimental design of the thermal analysis parameters were considered including sample size, flowing atmosphere, sample pan, and heating rate for both DSC and TG. The results established the optimum conditions for minimizing heat and mass transfer effect. Sample sizes used were: (5?C15?mg) for DSC and (30?C50?mg) for TG. DSC analysis used crimped crucibles with a pinhole, which allowed maximum resolution and gave well-defined mass (water) loss. TG analysis used a heating rate of 10?°C/min^?1 in an atmosphere of nitrogen. The heat of crystallization, heat of fusion, and heat of vaporization of unbound water are 334, 334, and 2,257?Jg^?1, respectively (Mitra et al. Proc NATAS Annu Conf Therm Anal Appl 30:203?C208, 2002). The DSC average water content of (MoM) was 80?wt% for name brand and 89.5?wt% for generic brand, based on the relative crystallization, melting and vaporization heats/Jg^?1 of distilled water in the recently purchased (2011) MoM samples. The TG showed a two-step process, losing water at 80?C135?°C for unbound water and bound water (MgO·H₂O) at 376?C404?°C, yielding a total average water loss of 91.9?% for name brand and 90.7?% for generic brand by mass. The difference between the high-temperature TG and the lower-temperature DSC can be attributed for the decomposition of magnesium hydroxide or MgO·H₂O. Therefore in performing this new approach to water analysis by heating to a high temperature decomposed the magnesium hydroxide residue. It was determined that the TG method was the most accurate for determining bound and unbound water.     

Substituent effects in double-helical hydrogen-bonded AAA-DDD complexes

Two series of DDD and AAA hydrogen-bond arrays were synthesized that form triply-hydrogen-bonded double-helical complexes when combined in CDCl(3) solution. Derivatization of the DDD arrays with electron-withdrawing groups increases the complex association constants by up to a factor of 30 in those arrays examined. Derivatization of the AAA arrays with electron donating substituents reveals a similar magnitude effect on the complex stabilities. The effect of substitution on both types of arrays are modeled quite satisfactorily (R(2) > 0.96 in all cases) as free energy relationships with respect to the sums of their Hammett substituent constants. In all, the complex stabilities can be manipulated over more than three orders of magnitude (>20 kJ mol(-1)) using this type of modification.     

New Chemodosimetric Reagents as Ratiometric Probes for Cysteine and Homocysteine and Possible Detection in Living Cells and in Blood Plasma

In this work, we have rationally designed and synthesized two new reagents ( L₁ and L₂ ), each bearing a pendant aldehyde functionality. This aldehyde group can take part in cyclization reactions with β‐ or γ‐amino thiols to yield the corresponding thiazolidine and thiazinane derivatives, respectively. The intramolecular charge‐transfer (ICT) bands of these thiazolidine and thiazinane derivatives are distinctly different from those of the molecular probes ( L₁ and L₂ ). Such changes could serve as a potential platform for using L₁ and L₂ as new colorimetric/fluorogenic as well as ratiometric sensors for cysteine (Cys) and homocysteine (Hcy) under physiological conditions. Both reagents proved to be specific towards Cys and Hcy even in the presence of various amino acids, glucose, and DNA. Importantly, these two chemodosimetric reagents could be used for the quantitative detection of Cys present in blood plasma by using a pre‐column HPLC technique. Such examples are not common in contemporary literature. MTT assay studies have revealed that these probes have low cytotoxicity. Confocal laser scanning micrographs of cells demonstrated that these probes could penetrate cell membranes and could be used to detect intracellular Cys/Hcy present within living cells. Thus, the results presented in this article not only demonstrate the efficiency and specificity of two ratiometric chemodosimeter molecules for the quantitative detection of Cys and Hcy, but also provide a strategy for developing reagents for analysis of these vital amino acids in biological samples.     

Photophysical and photodynamical study of fluoroquinolone drug molecule in bile salt aggregates

Photophysical properties of two widely used antibiotic fluoroquinolone drugs, namely Norfloxacin (NOR) and Ofloxacin (OFL) have been investigated in biomimicking environments formed by bile salts. Experimental results demonstrate that photophysical enhancement and fall of a particular prototropic species are sensitive to the excitation wavelength in bile salt aggregates. Excitation at shorter wavelengths reveals quenching of fluorescence of these fluoroquinolone with addition of sodium deoxycholate (NaDC), sodium taurocholate (NaTC) and sodium glycodeoxycholate (NaGDC). On the contrary, we observe a steady increase in the fluorescence intensity with a continuous redshift upon excitation at longer wavelength. The experimental results were rationalized in terms of the fact that, neutral and zwitterionic species of fluoroquinolone molecules in bile salt aggregates are selectively excited at shorter wavelength while the cationic form of fluoroquinolone molecules are excited at longer wavelength. The excess hydronium ions in the hydrophilic surface of bile salt aggregates convert the neutral species of NOR and OFL into cationic species causing an enhancement in the emission intensity. We found that NaGDC and NaTC because of the conjugate head group are more effective in converting the neutral species of fluoroquinolones into a cationic species than NaDC. The quenching order is in accordance with hydrophobicity indices of bile salt.     

Binomial and factorial congruences for Fq[t]

We present several elementary theorems, observations and questions related to the theme of congruences satisfied by binomial coefficients and factorials modulo primes (or prime powers) in the setting of polynomial ring over a finite field. When we look at the factorial of n or the binomial coefficient ‘n choose m’ in this setting, though the values are in a function field, n and m can be usual integers, polynomials or mixed. Thus there are several interesting analogs of the well-known theorems of Lucas, Wilson etc. with quite different proofs and new phenomena.     

Growth and characterization of borono phenylalanine

Borono phenylalanine abbreviated as BPA is a biologically important compound which is obtained from L‐Phenylalanine (C₉H₁₁NO₂) in which a boron atom is bonded. BPA is an amino acid analogue, helpful in the treatment of glioblastoma multiforme, a highly malignant form of brain tumor is crystallized in silica gel under pH 6.0 by single diffusion method in a period of 30 minutes. The grown crystals were characterized by x‐ray powder diffraction, Fourier Transform infrared spectroscopy and visible ultraviolet spectroscopy. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Determination of plutonium by secondary coulometric titration with internally generated iron(II)

The method for plutonium determination based on secondary controlled-potential coulometry, as described by SHULTS, is applied for analysis in the range of 0.1–5 mg plutonium. The method involves the oxidation of plutonium to Pu(VI) with perchloric acid followed by its reduction by an internally generated ferrous mediator. This is a two step procedure, involving the reduction of Pu(VI) and Fe(III) to a mixture of Pu(III) and Fe(II), followed by the oxidation of Pu(III) and Fe(II) to Pu(IV) and Fe(III), respectively. The net results is the reduction of Pu(VI) to Pu(IV), measured as the difference between the currents consumed during the reduction and oxidation steps. The original method of SHULTS involves 10–25 mg plutonium for each determination. Since the present method is intended for the analysis of smaller amounts of plutonium, the oxidation procedure described in the original version had to be modified. The method is found to work satisfactorily with a precision better than 0.1% at 5 mg level and 1.2% for 0.1 mg plutonium.     

Solvent extraction of Ni(II) from sulfate solutions with LIX 84I: flow-sheet for the separation of Cu(II), Ni(II) and Zn(II).

This paper reports on solvent-extraction studies of Ni(II) from sulfate solutions with LIX 84I (2-hydroxy-5-nonylacetophenoneoxime) as the extractant. The extraction of metal depends on the equilibrium pH of the aqueous phase and the extractant concentration. The transfer of metal follows a cation exchange-type mechanism: Ni2+ + 2HA --> NiA2 + 2H+. Extraction varies with the nature of the diluents. Temperature has no effect on the extraction of metal. The extraction behavior of associated metals clearly demonstrates the application of LIX 84I as the extractant for the separation of Cu(II), Ni(II) and Zn(II). Based on the results, a flow sheet of the process was developed.