Synthesis of a cyclic peptide/protein using the NEXT-A reaction followed by cyclization

By using the NEXT-A reaction, we introduced a non-natural amino acid at the N-terminus of a peptide/protein that contained a cysteine unit. The side chain of the introduced amino acid spontaneously reacted with the cysteine to afford a cyclic peptide/protein.     

Flow transition within an evaporating binary mixture sessile drop

The flow field along the base of an evaporating ethanol-water droplet and its evolution time was measured by particle image velocimetry. Three stages are revealed, a first stage dominated by multiple vortices, a second transition stage characterized by a remarkable spike in outward flow not previously identified, and a third stage dominated by outward flow identical to that found for pure water. Stage I is thought to be driven by surface tension gradients arising from local concentration variation. The spike in outward flow is explained in terms of a transition corresponding to almost total depletion of ethanol. An exponential decay in vorticity during the transition stage is explained in terms of ethanol diffusion from the bulk to the interface. We speculate on the existence of a zero-concentration wave propagating from the apex to the contact line corresponding to the final total depletion of ethanol.     

Sharp Hardy-Leray inequality for curl-free fields with a remainder term

In this paper, we give a new and a simpler approach to the result in [8] concerning the best constant of Hardy-Leray inequality for curl-free fields. As a by-product, we obtain an improved inequality with a remainder term. The non-attainability of the best constant is an easy consequence of the new inequality. The proof is based on a decomposition of curl-free fields into radial and spherical parts.     

A fluorous Mukaiyama coupling reagent for a concise condensation reaction: utility of medium-fluorous strategy

The entire study of condensation reactions using various fluorous Mukaiyama reagents, including a novel medium-fluorous strategy, is described. A Mukaiyama reagent bearing a medium-fluorous content tag, between 40 and 60% fluorine by weight, was prepared and examined in ester and amide-forming condensation reactions. At the end of the reactions, the fluorous pyridone by-product was effectively separated from non-fluorous components by increasing the water content of the crude reaction mixture and subsequent filtration of the precipitate. It is also shown that Mukaiyama reagents bearing a fluorous tag increase the reaction rate considerably when compared to their non-fluorous tagged counterpart. Interestingly, it was observed that the longer the fluorous chain, the higher the activity of the Mukaiyama reagent.     

Mid-infrared second-order susceptibility of alpha-quartz and its application to visible-infrared surface sum-frequency spectroscopy

We provide the first account of the second-order susceptibility of quartz down to 10 mum (1000 cm(-1)) and show how this data may be used along with the sum-frequency response of an amorphous gold surface to elucidate the nonlinear susceptibility of any material in the mid-infrared region. Crystalline quartz is an established material for use in second-harmonic and sum-frequency generation studies of new systems, on account of its well-characterized linear and nonlinear optical properties. Previous knowledge of its nonlinear susceptibility has been limited to its transparent region, wavelengths shorter than about 3 mum. Longer wavelength chi((2)) values for quartz are particularly important for techniques such as vibrational sum-frequency spectroscopy which are expanding into the mid-IR with the increasing availability of widely tunable infrared laser sources.     

Denitrohydrogenation of aliphatic nitro compounds and a new use of aliphatic nitro compounds as radical precursors

Aliphatic nitro groups are replaced by hydrogen on treatment with tributyltin hydride which proceeds via free radical chain processes. As the nitro group is selectively denitrated and other reducible groups are not affected with tributyltin hydride, this reaction can be used as a method for removing the nitro group from polyfunctional compounds. The radical intermediates generated via denitration can be also used for the carbon-carbon bond forming reactions.     

A novel and concise synthesis of spirodienone alkaloids using hypervalent iodine(III) reagents

Intramolecular oxidative coupling reaction of N-protected benzyltetrahydroisoquinoline derivatives using hypervalent iodine(III) reagents was investigated. The use of remarkable combination of phenyliodine bis (trifluoroacetate) (PIFA) and heteropoly acid (HPA) in wet acetonitrile smoothly afforded morphinandienone alkaloids, while neospirinedienone alkaloids were obtained in high yield under anhydrous conditions.     

Coexisting wobbling and quasiparticle excitations in the triaxial potential well of 163 Lu

High-spin states of the nucleus ¹⁶³Lu have been populated through the fusion-evaporation reaction ¹³⁹La(²⁹Si, 5n) with a beam energy of 157 MeV. In addition to the two lowest excited triaxial strongly deformed (TSD) bands, recently interpreted as one- and two-phonon wobbling excitations, a third excited TSD band has been firmly established decaying to the yrast TSD band. The assignment of this band as a three-quasiparticle band shows together with the normal deformed (ND) level scheme the presence not only of shape coexistence between ND and TSD structures, but also an interplay of wobbling and quasiparticle excitations in the triaxial strongly deformed potential well of ¹⁶³Lu.Received: 18 July 2003, Revised: 28 August 2003, Published online: 23 December 2003PACS: 21.10.-k Properties of nuclei; nuclear energy levels - 23.20.Lv transitions and level energies - 25.70.-z Low and intermediate energy heavy-ion reactions - 27.70. + q H. Amro: Present address: Wright Nuclear Structure Laboratory, Yale University, New Haven, CT 06520-8124, USA.     

Pair field of the yrast state with quadrupole pairing (Y21 and Y22)

We investigate the pair field of the yrast states in rotating nuclei including the terms with the symmetry Y₂₁ and Y₂₂ in addition to the monopole pairing term. The effect of the inclusion of the Y₂₁ and Y₂₂ terms on the Mottelson-Valatin effect is examined.