Finite-bandwidth effects on the causal prediction of ultrasonic attenuation of the power-law form

Kramers-Kronig (K-K) relations exist as a consequence of causality, placing nonlocal constraints on the relationship between dispersion and absorption. The finite-bandwidth method of applying these relations is examined where the K-K integrals are restricted to the spectrum of the experimental data. These finite-bandwidth K-K relations are known to work with resonant-type data and here are applied to dispersion data consistent with a power-law attenuation coefficient (exponent from 1 to 2). Bandwidth-restricted forms of the zero and once-subtracted K-K relations are used to determine the attenuation coefficient from phase velocity. Analytically, it is shown that these transforms produce the proper power-law form of the attenuation coefficient as a stand-alone term summed with artifacts that are dependent on the integration limits. Calculations are performed to demonstrate how these finite-bandwidth artifacts affect the K-K predictions under a variety of conditions. The predictions are studied in a local context as a function of subtraction frequency, bandwidth, and power-law exponent. The K-K predictions of the power-law exponent within various decades of the spectrum are also examined. In general, the agreement between finite-bandwidth K-K predictions and exact values grows as the power-law exponent approaches 1 and with increasing bandwidth.     

Rearrangements of pyrrole and indole substituted enol esters of cyclohexane-1,3-dione

Enol esters 3a and 3b , from cyclohexane-1,3-dione and pyrrole-2-carbonyl chloride and indole-2-carbonyl chloride, respectively, rearranged in the presence of triethylamine to the enamino acids 7 and 12 . In the presence of cyanide, 3b , also underwent the expected rearrangement to 4b , whereas only 7 was formed from 3a . Treatment of 7 with mercuric acetate in hot acetic acid resulted in decarboxylation and aromatization to phenol 9 .     

Novel natural products from soil DNA libraries in a streptomycete host

As a route to accessing the potential chemical diversity of uncultivable microbes from the soil, combinatorial biosynthetic libraries were constructed by cloning large fragments of DNA isolated from soil into a Streptomyces lividans host. Four novel compounds, terragines A (1), B (2), C (3), and D (4), were isolated from recombinant 436-s4-5b1, and another novel compound, terragine E (5), was isolated from 446-s3-102g1. The structures were determined by a combination of spectroscopic techniques, primarily 2D NMR.     

Contributions of methionine to recognition of trimethyllysine in aromatic cage of PHD domains: implications of polarizability,hydrophobicity, and charge on binding

Recognition of trimethyllysine (Kme3) by reader proteins is an important regulator of gene expression. This recognition event is mediated by an aromatic cage made up of 2–4 aromatic residues in the reader proteins that bind Kme3 via cation–π interactions. A small subset of reader proteins contain a methionine (Met) residue in place of an aromatic sidechain in the binding pocket. The unique role of sulfur in molecular recognition has been demonstrated in a number of noncovalent interactions recently, including interactions of thiols, thioethers, and sulfoxides with aromatic rings. However, the interaction of a thioether with an ammonium ion has not previously been investigated and the role of Met in binding Kme3 has not yet been explored. Herein, we systematically vary the Met in two reader proteins, DIDO1 and TAF3, and the ligand, Kme3 or its neutral analog tert-butyl norleucine (tBuNle), to determine the role of Met in the recognition of the cationic Kme3. Our studies demonstrate that Met contributes to binding via dispersion forces, with about an equal contribution to binding Kme3 and tBuNle, indicating that electrostatic interactions do not play a role. During the course of these studies, we also discovered that DIDO1 exhibits equivalent binding to tBuNle and Kme3 through a change in the mechanism of binding.

A conserved methionine in a trimethyllysine (Kme3) reader protein interacts via dispersion forces rather than ion-dipole interactions or the hydrophobic effect. Differences in selectivity for Kme3 versus its neutral analog were also discovered.     

Preparation of a clinically investigated ras farnesyl transferase inhibitor

The synthesis of ras farnesyl‐protein transferase inhibitor 1 is described on a multi‐kilogram scale. Retrosynthetic analysis reveals chloromethylimidazole 2 and a piperazinone 3 as viable precursors. The 1,5‐disubstituted imidazole system was regioselectively assembled via an improved Marckwald imidazole synthesis. A new imidazole dethionation procedure has been developed to convert the Marckwald mercaptoim‐idazole product to the desired imidazole. This methodology was found to be tolerant of a variety of functional groups providing good to excellent yields of 1,5‐disubstituted imidazoles. A new Mitsunobu cycliza‐tion strategy was developed to prepare the arylpiperazinone fragment 3 .     

A zirconium zwitterion containing a caged amine H atom

The crystallographically centrosymmetric zwitterion bis­[tris(3,5‐di­methyl‐2‐oxidobenzyl‐κO)­ammonium]­zirconium(IV) crystallizes as the chloro­form disolvate, [Zr(C₂₇H₃₁NO₃)₂]·2CHCl₃, with the two mol­ecules of chloro­form closely associated with two of the aromatic rings. The Zr atom has a distorted octahedral geometry with three phenoxy O atoms from each of the two ligands coordinated to it. Charge balance is maintained by protonation of each N atom, which then forms intramolecular hydrogen‐bonding interactions to all three adjacent O atoms.     

Transient elastohydrodynamic drag on a particle moving near a deformable wall

We examine the prescribed time-dependent motion of a rigid particle(a sphere or a cylinder) moving in a viscous fluid close toa deformable wall. The fluid motion is described by a nonlinearevolution equation, derived using lubrication theory, whichis solved using numerical and asymptotic methods; a local linearpressure–displacement model describes the wall. When theparticle moves from rest towards the wall, fluid trapping beneaththe particle leads to an overshoot in the normal force on theparticle; a similarity solution is used to describe trappingat early times and a multiregion asymptotic structure describesfluid draining at late times. When the particle is pulled fromrest away from the wall, a peeling process (described by a quasisteadytravelling wave) determines the rate at which fluid can enterthe growing gap between the particle and the wall, leading toa transient adhesive normal force. When a cylinder moves fromrest transversely over the wall, transient peeling motion isagain observed (especially when the wall is initially indented),giving rise to an overshoot in the transverse drag. Simulationsfor a translating sphere show highly nonlinear wall deformationscharacterized by a localized crescent-shaped ridge. Despitegenerating sharp transient deformations, we found no numericalevidence of finite-time choking events.     

Genetic analysis of posterior medial barrel subfield (PMBSF) size in somatosensory cortex (SI) in recombinant inbred strains of mice

Background  

Quantitative trait locus (QTL) mapping is an important tool for identifying potential candidate genes linked to complex traits. QTL mapping has been used to identify genes associated with cytoarchitecture, cell number, brain size, and brain volume. Previously, QTL mapping was utilized to examine variation of barrel field size in the somatosensory cortex in a limited number of recombinant inbred (RI) strains of mice. In order to further elucidate the underlying natural variation in mouse primary somatosensory cortex, we measured the size of the posterior medial barrel subfield (PMBSF), associated with the representation of the large mystacial vibrissae, in an expanded sample set that included 42 BXD RI strains, two parental strains (C57BL/6J and DBA/2J), and one F1 strain (B6D2F1). Cytochrome oxidase labeling was used to visualize barrels within the PMBSF.     

Search for new particles decaying to t&tmacr; in p&pmacr; collisions at radicals = 1.8 TeV

We use 106 pb (-1) of data collected with the Collider Detector at Fermilab to search for narrow-width, vector particles decaying to a top and an antitop quark. Model independent upper limits on the cross section for narrow, vector resonances decaying to t&tmacr; are presented. At the 95% confidence level, we exclude the existence of a leptophobic Z' boson in a model of top-color-assisted technicolor with mass M(Z')<480 GeV/c(2) for natural width gamma = 0.012M(Z'), and M(Z')<780 GeV/c(2) for gamma = 0.04M(Z').