Observation of intermolecular interactions in large protein complexes by 2D-double difference nuclear Overhauser enhancement spectroscopy: application to the 44 kDa interferon-receptor complex

NMR detection of intermolecular interactions between protons in large protein complexes is very challenging because it is difficult to distinguish between weak NOEs from intermolecular interactions and the much larger number of strong intramolecular NOEs. This challenging task is exacerbated by the decrease in signal-to-noise ratio in the often used isotope-edited and isotope-filtered experiments as a result of enhanced T(2) relaxation. Here, we calculate a double difference spectrum that shows exclusively intermolecular NOEs and manifests the good signal-to-noise ratio in 2D homonuclear NOESY spectra even for large proteins. The method is straightforward and results in a complete picture of all intermolecular interactions involving non exchangeable protons. Ninety-seven such (1)H-(1)H NOEs were assigned for the 44 KDa interferon-α2/IFNAR2 complex and used for docking these two proteins. The symmetry of the difference spectrum, its superb resolution, and unprecedented signal-to-noise ratio in this large protein/receptor complex suggest that this method is generally applicable to study large biopolymeric complexes.     

An interpolation problem in the class of stieltjes functions and its connection with other problems

This paper contains the proofs and some development of results that were published without proofs in [KN2]. It is completed with comments added by the second author explaining how these results became the basis of statements and the solutions of problems in the theory of entire functions, in the moment problem, in direct and inverse problems of the spectral theory of nonhomogeneous strings and in other problems.     

Photokinetics of two novel photochromic diarylethenes derived from benzothiophene

Two new unsymmetrically substituted photochromic diarylethenes, namely 3‐[3, 3,4,4,5,5‐hexafluoro‐2‐(2‐methylbenzothien‐3‐yl)cyclopent‐1‐en‐1‐yl]‐2‐methyl‐6‐methoxy‐1‐ benzothiophene and 3‐[3,3,4,4,5,5‐hexafluoro‐2‐(2‐methylbenzothien‐3‐yl)cyclopent‐1‐en‐1‐yl]‐2‐methyl‐6‐methoxy‐7‐nitro‐1‐benzothiophene, were synthesized. Their optical properties and kinetics of cyclization and cycloreversion were determined in four solvents and compared with the symmetrical diarylethene (3,3,4,4,5,5‐hexafluorocyclopent‐1‐en‐1,2‐diyl)bis(2‐methyl‐1‐benzothiophene). While the UV spectra of the three compounds are almost insensitive to solvent changes, the rates of the ring‐opening and ring‐closure reactions exhibit interesting kinetic behavior that differs from other diarylethenes reported in the literature. The cycloreversion for the three compounds follows first‐order kinetics, whereas the cyclization cannot be described by a simple kinetic law. Different approaches were tested, and a complex exponential equation could be derived that fits the experimental data. The unusual presence of two ring‐opened conformational isomers, one of them nonphotochromic, is proposed for the ring‐opened compounds to explain the derived kinetic law and observed solvent effects. These results are of interest in relation to the application of the novel diarylethenes as potential optical materials. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 736–744, 2012     

Acetyl Chloride-Methanol as a Convenient Reagent for: A) Quantitative Formation of Amine Hydrochlorides B) Carboxylate Ester Formation C) Mild Removal of N-t-Boc-Protective Group.

Hydrogen chloride qualitatively generated in situ by the addition of acetyl chloride to alcoholic solutions is a useful reagent for carboxylic acid esterification, N-t-Boc deprotection and phosphoramide solvolysis reactions.     

The Hochschild homology of fatpoints

This paper calculates the Hochschild homology of fatpoints—rings of the formk[x ₁,x ₂,…,x _d ]/m ^a wherek is a field of characteristic zero and m=(x ₁ x ₂,…,x _d ). The calculation includes the multiplicative structure induced by the shuffle product. The answer is given in terms of the homology of tori relative to theira-diagonal. Since the rings in question are monoidal, this calculation also determines their topological Hochschild homology. By a theorem of Goodwillie, the dimensions of the cyclic homology groups of these rings are determined as well.