摘要：The chemistry of carbon-centered free radicals is only perturbed to a minor extent by the presence of β-hydroxy and β-alkoxy groups. The β-ethoxyethyl radical (1) preferentially adopts a staggered condormation with the C-O bond synclinal to the axis of the half-filled p-orbital.
摘要：The sign of the ~1L_b Cotton effects (ECs) of the benzene chromophore from about 240 to 270 nm in the circular dichroism (CD) of enantiomers of ring-substituted chiral benzylcarbinamines and benzylcarbinamine salts are correlated with their absolute configurations using the benzene sector rule and a consideration of the equilibrium between their two conformers of lowest energy and of oppositely signed rotatory power.
摘要：Concentrated sulfuric acid readily protonates organic mol- ecules with oxygen-containing functional groups. This pro- tonation is often strongly exothermic and shifts equilibrium between gaseous and dissolved species toward the solvated state. To dissolve in the acid, an approaching gas molecule must first collide with the acid's surface. The molecule may then scatter inelastically from the surface or bind momentarily to interfacial H_2SO_4 before evaporating or remaining behind.
摘要：The electronic spectrum of the blue copper protein plastocyanin has been studied by ab initio multiconfigurational second-order perturbation theory (the CASPT2 method). The six lowest electronic transitions have been calculated and assigned with an error of less than 2000 cm~-1. The singly occupied orbital in the ground state is Cu 3d-Scys 3pπ antibonding with some N_His 2pσ character.
摘要：Experimental details are given for the preparation of "softballs", large self-complementary molecules capable of assembly into pseudo-spherical capsules. Evidence is presented for their existence as hydrogen bonded dimmers in organic solvents, and binding affinities for the reversible encapsulation of smaller molecules of suitable size and shpe are given. Studies at various temperatures result in calculated enthalpies and entropies of encapsulation that are positive; accordingly, the process is entropy driven.
摘要：The results presented in this paper show that accurate through-space internuclear distance measurements can be performed on doubly labeled retinals using the one-dimensional approach to the solid state magic angle spinning (MAS) rotational resonance NMR technique.
摘要：The many special physical properties of water have been obvious for many years. We are interested here in shear relaxation dynamics at solid surfaces-a topic directly relevant to electrochemistry and corrosion, soil science, geophysics, and colloidal suspensions, and with possible ramifications for understanding vicinal water at lipids and proteins.
摘要：The correlation between hydrogen/deuteriumα-secondary kinetic isotope effects and transition state looseness has been investigated by MP2/6-31+ + G(d, p) calculations on three identity X~_ + CH_3X Sn2 reactions. By varying the C-X distances in these systems it is shown that the secondary kinetic isotope effect increases with increasing transition structure looseness.
摘要：A sequence of ordered solvent peaks in the electron density map of the minor groove region of ApT-rich tracts of the double helix is a characteristic of B-form DNA well established from crystallography. This feature, termed the "spine of hydration", has been discussed as a stabilizing feature of B-DNA, the structure of which is known to be sensitive to environmental effects.
摘要：High-level ab initio computations were used to characterize the parent species and ~αC radicals for alanine, serine, and threonine, both as free neutral amino acids (AH) and as residues in model peptides (PH) intended to mimic the midchain environment in proteins.
摘要：The absolute configuration of curacin A was determined as (2R, 13R, 19R, 21S)-1 by comparison of degradation products 2 and 3 with the same materials prepared by asymmetric synthesis. The total synthesis of 1 was completed from (1R, 2S)-2-methylcyclopropanecarboxylic acid (8) and the amino alcohol derivative 46. The latter was prepared from 4-pentynal (14) and the Garner aldehyde (43).
摘要：Stabilized 1, 2-dioxetanes which are enzymatically triggered to undergo chemiluminescent decomposition are widely used in numerous applications including immunoassays, gene expres- sion studies, Western blotting, Southern blotting, DNA sequenc- ing, and the identification of infectious agents.
摘要：Electron spectroscopic and diffraction results obtained in ultra-high-vacuum, combined with cyclic voltammetric data, are reported for sulfur adlayers deposited from aqueous sulfide and bisulfide media on Pt(111). The highest coverage obtained by Auger electron spectroscopy, 0.94+ -0.05 monolayer, is very close to the coverage obtained from coulometry, and is associated with a (1*1) surface phase.
摘要：Enzyme structure and function have been studied for subtilisin NPB' solubilized in organic solvents solvents by ion pairing with low concentrations of an anionic surfactant (Aerosol OT) in the absence of reversed micelles. Soluble subtilisin shows strikingly different behavior in octane and tetrahydrofuran (THF). In octane, the K_cat/K_m for the transesterification of N-acetyl-L-phenylalanine ethyl ester (APEE) is 370 M~-1S~-1, within one order of magnitude of the enzyme's hydrolytic activity in water.
摘要：The transition state for NAD~+ (oxidized nicotinamide adenine dinucleotide) hydrolysis by the cholera toxin Al polypeptide (CTA) has been characterized by multiple V/K kinetic isotope effects (KIEs) using labeled NAD~+ as the substrate. CTA causes cholera by catalyzing the ADP-ribosylation of the signal-transducing G_Sα protein.
摘要：Since the first reported example of the preparation of an organic monolayer on a cuprate-based high-temperature super- conductor (HTSC), a great deal has been learned about the utility of these new surface structures for tailoring HTSC surface and interfacial properties. Monolayers on HTSCs have been used as hydrophobic layers for corrosion passivation and as prelayers for polymer adhesion and nucleation.
摘要：Quenching of the luminescent excited state of Eu~3+ ions by C-H high-vibrational modes was studied by deuteration of the encapsulating ligand and the solvent. Novel polydentate hemispherands providing nine donor atoms, which from overall neutral complexes with rare earth ions, were synthesized in nine steps, allowing the easy incorporation of deuterium atoms (11a-d. Eu~3+).
摘要：Microperoxidase-8 (MP8) is the heme octapeptide from enzymatic proteolysis of horse-heart cytochrome C. Not only is MP8 a functional peroxidase (it catalyzes the oxidation of various substrates by hydrogen peroxide), it has also served as a useful calibration for the interpretation of the electronic spectroscopic properties of heme proteins. NMR structural characterization of MP8 has been difficult, owing to extensive aggregation at millimolar concentrations.
摘要：Photolysis of dibenzothiophene sulfoxide results in the formation of dibenzothiophene and oxidized solvent. Though quantum yields are low, chemical yields of the sulfide are quite high. Yields of the oxidized solvents can also be high. Typical products are phenol from benzene, cyclohexanol, and cyclohexene from cyclohexane and 2-cyclohexenol and epoxycyclohexane from cyclohexene.
摘要：A series of linear peptides designed to fold into differentβ-hairpin conformation in aqueous solution has been studied by ~1H NMR with the aim of understanding the role played by the turn residue sequence in defining β-hairpin structure. The designed peptides differ only in the amino acid sequence of the putative turn region and have identical strand residues.