Picosecond thermometer in the amide I band of myoglobin

The amide I and II bands in myoglobin show a heterogeneous temperature dependence, with bands at 6.17 and 6.43 microm which are more intense at low temperatures. The amide I band temperature dependence is on the long wavelength edge of the band, while the short wavelength side has almost no temperature dependence. We compare concepts of anharmonic solid-state crystal physics and chemical physics for the origins of these bands. We suggest that the long wavelength side is composed of those amino acids which hydrogen bond to the hydration shell of the protein, and that temperature dependent bands can be used to determine the time it takes vibrational energy to flow into the hydration shell. We determine that vibrational energy flow to the hydration shell from the amide I takes approximately 20 ps to occur.     

Evidence for nontermination of rotational bands in 74Kr

Three rotational bands in 74Kr were studied up to (in one case one transition short of) the maximum spin I(max) of their respective single-particle configurations. Their lifetimes have been determined using the Doppler-shift attenuation method. The deduced transition quadrupole moments reveal a modest decrease, but far from a complete loss of collectivity at the maximum spin I(max). This feature, together with the results of mean field calculations, indicates that the observed bands do not terminate at I = I(max).     

Photochemical pinacol rearrangements of unsymmetrical diols

The photochemical pinacol reaction of a series of nonsymmetrical 9-fluorenyl-substituted vic-diols was investigated and compared with their acid-catalyzed thermal reaction. Unlike the thermal reaction, the radiation-induced processes involve only fluorenyl cations, as is reflected in differences of product distribution between the two reactions. From the product studies, substituent migratory aptitudes are reversed in the photochemical process, suggesting that kinetic control takes place under neutral conditions unlike the acid-catalyzed thermal reactions. The presence of fluorenyl cation intermediates and their lifetimes were established by laser flash spectroscopy studies.     

A transient N-O-linked Pauson-Khand strategy for the synthesis of the deschloro carbocyclic core of the palau'amines and styloguanidines

A stereocontrolled route to the deschloro cyclopentyl core of the palau'amines and styloguanidines has been developed. This strategy makes use of the intramolecular Pauson-Khand cyclization of an enyne with a "transient N-O tether" to construct a five-membered carbocycle in a diastereoselective fashion. [reaction: see text]     

High-spin structure of N\simeq Z nuclei around the A = 72 region

High-spin states have been studied in ⁷²Kr and ⁷²Br using the ⁴⁰Ca + ⁴⁰Ca and ³⁶Ar + ⁴⁰Ca reactions at 164 and 145 MeV, respectively. The properties and configurations of the high-spin bands observed have been interpreted using unpaired cranked Nilsson-Strutinsky (CNS), and for ⁷²Kr, paired cranked relativistic Hartree-Bogoliubov (CRHB) calculations. In ⁷²Kr a new band has been identified that has the properties expected for the doubly aligned S-band configuration. In ⁷²Br the previously known bands have been extended to higher spin. This has lead to a re-interpretation of the configurations.Received: 31 October 2002, Published online: 24 February 2004PACS: 21.10.Re Collective levels - 23.20.Lv transitions and level energies - 27.50. + e      

Time resolved collapse of a folding protein observed with small angle x-ray scattering

High-intensity, "pink" beam from an undulator was used in conjunction with microfabricated rapid-fluid mixing devices to monitor the early events in protein folding with time resolved small angle x-ray scattering. This Letter describes recent work on the protein bovine beta-lactoglobulin where collapse from an expanded to a compact set of states was directly observed on the millisecond time scale. The role of chain collapse, one of the initial stages of protein folding, is not currently understood. The characterization of transient, compact states is vital in assessing the validity of theories and models of the folding process.     

Structural investigation on PEO-based polymer electrolytes dispersed with Al<Subscript>2</Subscript>O<Subscript>3</Subscript> nanoparticles

Thin solid polymer electrolytes based on polyethylene oxide (PEO) and silver triflate (AgCF₃SO₃) dispersed with various concentrations of aluminum oxide (Al₂O₃) nanoparticles have been prepared by solution casting technique. These thin polymer films are found to have thickness of the order of 30 to 100 μm. The X-ray diffraction (XRD) patterns have indicated the amorphous nature of the polymer electrolyte. The differential scanning calorimeter (DSC) traces showed slight change in the glass transition temperature (T _g) whereas the degree of crystallization (X _c) decreases markedly due to the addition of alumina nanoparticles. Fourier transform infrared (FTIR) spectral analysis of all these samples has revealed the presence of absorption bands around 1,000 cm⁻¹; thus indicating the complexation of silver ions with oxygen in PEO. Employing the Wagner’s polarization technique as the standard method, the total ionic transference number for the complexed polymer electrolyte was found to be approximately unity thereby revealing that the significant contribution to electrical conduction was due to ions only. Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, December 7–9, 2006     

Two‐injection workflow for a liquid chromatography/LTQ‐Orbitrap system to complete in vivo biotransformation characterization: demonstration with buspirone metabolite identification

The relatively high background matrix in in vivo samples typically poses difficulties in drug metabolite identification, and causes repeated analytical runs on unit resolution liquid chromatography/mass spectrometry (LC/MS) systems before the completion of biotransformation characterization. Ballpark parameter settings for the LTQ‐Orbitrap are reported herein that enable complete in vivo metabolite identification within two HPLC/MS injections on the hybrid LTQ‐Orbitrap data collection system. By setting the FT survey full scan at 60K resolution to trigger five dependent LTQ MS² scans, and proper parameters of Repeat Duration, Exclusion Duration and Repeat Count for the first run (exploratory), the Orbitrap achieved the optimal parallel data acquisition capability and collected maximum number of product ion scans. Biotransformation knowledge based prediction played the key role in exact mass ion extraction and multiple mass defect filtration when the initial data was processed. Meanwhile, product ion extraction and neutral loss extraction of the initial dependent data provided additional bonus in identifying metabolites. With updated parent mass list and the data‐dependent setting to let only the ions on the parent mass list trigger dependent scans, the second run (confirmatory) ensures that all precursor ions of identified metabolites trigger not only dependent product ion scans, but also at or close to the highest concentration of the eluted metabolite peaks. This workflow has been developed for metabolite identification of in vivo or ADME studies, of which the samples typically contain a high level of complex matrix. However, due to the proprietary nature of the in vivo studies, this workflow is presented herein with in vitro buspirone sample incubated with human liver microsomes (HLM). The major HLM‐mediated biotransformation on buspirone was identified as oxidation or hydroxylation since five mono‐ (+16 Da), seven di‐ (+32 Da) and at least three tri‐oxygenated (+48 Da) metabolites were identified. Besides the metabolites 1‐pyrimidinylpiperazine (1‐PP) and hydroxylated 1‐PP that formed by N‐dealkylation, a new metabolite M308 was identified as the result of a second N‐dealkylation of the pyrimidine unit. Two new metabolites containing the 8‐butyl‐8‐azaspiro[4,5]decane‐7,9‐dione partial structure, M240 and M254, were also identified that were formed apparently due to the first N‐dealkylation of the 1‐PP moiety. Copyright © 2009 John Wiley & Sons, Ltd.