Facile synthesis of N‐α‐boc‐1,2‐dialkyl‐l‐histidines: Utility in the synthesis of thyrotropin‐releasing hormone (trh) analogs and evaluation of the cns activity

A facile synthesis of N‐α‐Boc‐1,2‐dialkyl‐L‐histidines starting from N‐α‐trifluoroacetyl‐L‐histidine methyl ester is reported. The key steps involve direct and regiospecific N‐1(τ) ring‐alkylation of the N‐α‐trifluoroacetyl‐L‐histidine‐methyl ester by suitable alkyl iodide in the presence of NaH in DMF at ?15 °C followed by homolytic free radical C‐2 alkylation via a silver catalyzed oxidative decarboxylation of alkylcarboxylic acid in the presence of ammonium persulfate under acidic conditions. The application of newly synthesized bioimidazoles was illustrated by their incorporation into thyrotropin‐releasing hormone (TRH). The synthesized TRH analogs were evaluated in vivo for analeptic activity. We report discovery of a TRH analog, which was found to potentiate the pentobarbital‐induced sleep in vivo.     

Chemoselective N-acylation via condensations of N-(benzoyloxy)amines and alpha-ketophosphonic acids under aqueous conditions

A new amide-forming reaction with N-benzoyloxyamines and alpha-ketophosphonic acids was investigated. A mixed solvent of t-BuOH/water (1:1) at 40 degrees C provided the desired amide in high yield (71-96%). Both phosphonic acids ( 9, 12, or 13) and their disodium salts (e.g., 10) were shown to react with the respective N-benzoyloxyamines ( 1b and 4) in excellent yields. The phosphonic acid methyl ester monosodium salt 11 did not react under these conditions. However, compound 11 did provide the desired amide in 22% yield upon addition of 2 equiv of TFA. The N-acylation reaction is highly chemoselective for N-benzoyloxyamines as both aliphatic amines and N-hydroxylamines were shown not to react productively with the alpha-ketophosphonic acids under the conditions tested. Moreover, the alpha-ketophosphonic acids are more selective than the related alpha-ketocarboxylic acid systems, which react with both the N-hydroxylamines and N-benzoyloxyamines. In this regard, this novel phosphonic acid methodology provides a new high-yielding, chemoselective acylating reagent for further study.     

Near-IR region absorbing 1,4-diaminoanthracene-9,10-dione motif based ratiometric chemosensors for Cu

1,4-Bis[2-aminoethylamino]anthracene-9,10-diones selectively bind with Cu²⁺ to form complexes with unusual selectivity under basic conditions. The deprotonation of the aryl amine NH in the case of these chemosensors causes a bathochromic shift in the absorption band from 585 nm and 635 nm to 725 nm and enables ratiometric estimation of Cu²⁺ between pH 8 and 12.     

Surface plasmon resonance based fiber optic sensor utilizing indium oxide

A highly sensitive surface plasmon resonance (SPR) based fiber optic sensor with indium oxide (In₂O₃) layer coated on the core of the optical fiber is presented and theoretically analyzed. The sensitivity of the SPR based fiber optic sensor has been evaluated numerically. It is shown that the proposed SPR based fiber optic sensor with In₂O₃ layer possesses high sensitivity in the near infrared region of spectrum, which needs attention to many environmental and security applications and offers more accurate and highly reproducible measurements. In addition, the sensitivity of the SPR based fiber optic sensor decreases with the increase in the thickness of In₂O₃ layer. With sensitivity as high as 4600 nm/RIU, the 170 nm thick In₂O₃ layer based fiber optic SPR sensor demonstrates better performance.     

Purification,Characterisation and Cloning of a 2S Albumin with DNase,RNase and Antifungal Activities from Putranjiva Roxburghii

The present study reports the characterisation of a novel ~12-kDa heterodimeric protein, designated as putrin, from the seeds of Putranjiva roxburghii. The purification of putrin to homogeneity was accomplished using DEAE-sepharose where protein was unbound, CM-sepharose and Cibacron blue 3GA where it was bound and appeared as single peak on a size-exclusion chromatography column. A 15 % sodium dodecyl sulphate polyacrylamide electrophoresis gel, under reducing condition, demonstrated that putrin is made of two polypeptide chains of approximately 4.5 and 7.5 kDa. Circular dichroism studies demonstrated the helical nature and conformational stability of protein at increasing temperatures. Putrin exhibited both RNase and DNase activities and exerted antifungal activity but possessed relatively weak translation–inhibitory activity in cell-free system. The cloning and sequence analysis revealed a 414 bp open reading frame encoding a preproprotein of 137 amino acid residues. The amino acid sequence comparisons and phylogenetic analysis of putrin showed significant homology to 2S seed storage family proteins. The results demonstrated that putrin belongs to 2S albumin family and exhibits a spectrum of biotechnologically exploitable functions.     

A new antifungal eudesmanolide glycoside isolated from Sphaeranthus indicus Linn. (Family Compositae)

A new antifungal eudesmanolide glycoside 11,13-dihydro-3-O-(β-digitoxopyranose)-7α-hydroxy eudasman-6,12-olide (2) in addition to known compounds 1 and 3, has been isolated from Sphaeranthus indicus Linn. Its structure was determined by spectral analysis (UV, IR, 1D and 2D NMR and mass spectrum).     

Colorimetric recognition of Cu(II) by (2-dimethylaminoethyl)amino appended anthracene-9,10-diones in aqueous solutions: deprotonation of aryl amine NH responsible for colour changes

Chromogenic receptors 2 and 3 undergo distinct colour changes from magenta to blue on gradual addition of Cu(II) and can be used as colorimetric probes for spectrophotometric and visual analysis of Cu(II) in the presence of biological metal ions Na(I), K(I), Mg(II), Ca(II), Fe(II), Zn(II) etc. in aqueous solution (methanol-water 1 : 1 v/v). On addition of Cu(II), both 2 and 3 exhibit a bathochromic shift of Delta lambda(max) = 114 nm for 2 and Delta lambda(max)= 150 and 265 nm for receptor 3. The protonation constants and formation constants of Cu(II) complexes of receptors 2 and 3 (at pH 7) and the effect of pH on formation of these complexes has been determined by the combination of UV-vis-pH titrations of receptors 2 and 3 and their Cu(II) complexes. These results and the emergence of only one peak at 610 nm for 2 and two distinct absorption peaks at 715 and 800 nm for 3 on addition of Cu(II) unambiguously point to mono- and di-deprotonation for 2 and 3, respectively.     

Rietveld refinement and impedance spectroscopy of calcium titanate

Single phase perovskite CaTiO₃ has been synthesized by conventional solid state reaction technique. The ceramic was characterized by XRD at room temperature and its Rietveld refinement inferred orthorhombic crystal structure with the space group Pbnm. The field dependence of dielectric relaxation and conductivity was measured over a wide frequency range from room temperature to 673 K. Analysis of Nyquist plots of CaTiO₃ revealed the contribution of many electrically active regions corresponding to bulk mechanism, distribution of grain boundaries and electrode processes. The dc conductivity depicted a semiconductor to metal type transition. Frequency dependence of dielectric constant (ε′) and tangent loss (tan δ) show a dispersive behavior at low frequencies and is explained on basis of Maxwell-Wagner model and Koop's theory. Both conductivity and electric modulus formalisms have been employed to study the relaxation dynamics of charge carriers. The variation of ac conductivity with frequency at different temperatures obeys the universal Jonscher's power law (σ_ac α ω^s). The values of exponent ‘s’ lie in the range 0.13 ≤ s ≤ 0.33, which in light of CBH model suggest a large polaron hopping type of conduction mechanism.