Sensitive high resolution inverse detection NMR spectroscopy of proteins in the solid state

A new indirect detection scheme for obtaining (15)N/(1)H shift correlation spectra in crystalline proteins is described. Excellent water suppression is achieved without the need for pulsed field gradients, and using only a 2-step phase cycle. Careful attention to overall NMR instrument stability was found critical for obtaining the best resolution and sensitivity. Magnetic dilution by deuteration of the protein in combination with high-speed magic angle spinning produces (1)H resonances averaging only 0.22 ppm in width, and in some cases lines as narrow as 0.17 ppm are obtained. In application to two different polymorphs of ubiquitin, structure dependent differences in both (15)N and (1)H amide chemical shifts are observed. In one case, distinct shifts for different molecules in the asymmetric unit are seen, and all differ substantially from solution NMR shifts. A gain of 7 in sensitivity makes the method competitive with solution NMR as long as nanocrystalline samples are available.     

Fluorescent core-shell polymer particles containing luminophore dyes: synthesis and optical response to acetone

Monodisperse dye-containing crosslinked particles are promising for application in novel optical chemical sensors due to their intrinsic sensitivity. However, preparation of these particles in aqueous media still remains a challenge, since luminophores inhibit radical processes or else cannot embed into polymer chains because of difference in monomer reactivity ratios. In this work, novel dye-containing monodisperse crosslinked particles were prepared and characterized. In order to obtain dye-containing monodisperse crosslinked particles, we studied seed copolymerization of styrene in the presence of divinylbenzene. The influence of nature and concentration of the used comonomers and co-solvents on shape, size distributions and surface characteristics of the particles formed was investigated. Shapes and diameters of the particles were analyzed by DLS, TEM and SEM. The data of SEM and optical spectroscopy studies demonstrated that the synthesized particles were able to self-assemble into thin-film three-dimensional ordered structures. Finally, the structures under study are promising for development of sensor devices with optical response to acetone.     

Investigation of the mechanism of protein adsorption on ordered mesoporous silica using flow microcalorimetry

The adsorption of bovine serum albumin (BSA) and lysozyme (LYS) on siliceous SBA-15 with 24 nm pores was studied using flow microcalorimetry; this is the first attempt to understand the thermodynamics of protein adsorption on SBA-15 using flow microcalorimetry. The adsorption mechanism is a strong function of protein structure. Exothermic events were observed when protein–surface interactions were attractive. Entropy-driven endothermic events were also observed in some cases, resulting from lateral protein–protein interactions and conformational changes in the adsorbed protein. The magnitudes of the enthalpies of adsorption for primary protein–surface interactions decrease with increased surface coverage, indicating the possibility of increased repulsion between adsorbed protein molecules. Secondary exothermic events were observed for BSA adsorption, presumably due to secondary adsorption made possible by conformational changes in the soft BSA protein. These secondary adsorption events were not observed for lysozyme, which is structurally robust. The results of this study emphasize the influence of solution conditions and protein structure on conformational changes of the adsorbed protein and the value of calorimetry in understanding protein–surface interactions.     

Geometrical Molecular Structure Design Concept in Approach to Homo- and Heterometallic Precursors of Advanced Materials in Sol–Gel Technology

The article describes the principles of the Single Source Precursor approach to inorganic materials and introduces the Geometrical Molecular Structure Design Concept (MSDC) based on the choice of a proper molecular structure type for the desired precursor and completing it with ligands providing both the necessary number of donor atoms and the sterical protection of the chosen core. Application of MSDC is illustrated with examples taken from development of new approaches in the synthesis of oxide and sulfide catalysts and ferroelectric oxide materials.     

Sulfonimidamides and Imidosulfuric Diamides: Compounds from an Underexplored Part of Biologically Relevant Chemical Space

Two novel solid reagents—1-sulfonimidoyl- and 1-sulfamimidoyl-3-methylimidazolium derivatives—for the synthesis of sulfonimidamides and imidosulfuric diamides, respectively, were developed. It is shown that these reagents are very effective in substitution reactions with various N- and O-nucleophiles; therefore, they significantly extend the accessibility to the chemical space covered by organosulfur(VI) compounds with S=N bonds. In addition, previously unknown imidosulfuric diamides with free imino nitrogen groups were prepared, and their physical and chemical properties were characterized (including molecular geometry, pK_a, Log P, microsomal stability, and reactivity towards typical electrophiles). Similar to other organosulfur(VI) derivatives with S=N bonds, these compounds can be considered as promising bioisosteres of amides, ureas, or sulfonamides.     

K3Cr2(PS4)3: A New Chromium Thiophosphate with a One‐Dimensional [Cr2(PS4)]3— Anion Chain

A new chromium thiophosphate, K₃Cr₂(PS₄)₃ has been prepared and characterized by single‐crystal diffraction, temperature dependent magnetic susceptibility measurements and optical spectroscopy. K₃Cr₂(PS₄)₃ crystallizes in the monoclinic space group P2₁/n (No. 14) with a = 9.731(2) Å, b = 11.986(2) Å, c = 17.727(4) Å, β = 96.52(2)°, V = 2054.2(2) ų, Z = 4, and R = 0.044. The anionic part of the structure consists of dimeric Cr₂(μ₃‐S₃PS)₂ units which are linked by bidentate PS₄ groups to form infinite one‐dimensional [S₂P_S2Cr₂(μ₃S₃P_S)₂]^3— chains separated by K⁺ cations. The Cr^III centers of the Cr₂(μ₃‐S₃PS)₂ units are antiferromagnetically coupled. The magnetic susceptibility data may be fitted using a D‐Heisenberg model for S = 3/2 with g = 2.02 and J/k = 10K. K₃Cr₂(PS₄)₃ is semiconducting with an optical band gap of 1.35 eV.     

Controlling phase formation in solids: rational synthesis of phase separated Co@Fe2O3 heteroparticles and CoFe2O4 nanoparticles

A wet chemical approach from organometallic reactants allowed the targeted synthesis of Co@Fe(2)O(3) heterodimer and CoFe(2)O(4) ferrite nanoparticles. They display magnetic properties that are useful for magnetic MRI detection.     

Synthesis of Enantiomeric Aminophosphonic Acids and Peptides

Abstract

Synthesis of enantiomeric amino phosphonic acids APA is described by using chiral auxiliary reagent or enzymatic resolution of racemic mixtures of APA phenacyl derivatives. Peptides with APA residue were obtained by application of trimethylsilyl derivatives or condensation in the presence of enzyme-papain     

13C CPMAS spectroscopy of deuterated proteins: CP dynamics, line shapes, and T1 relaxation

(13)C CPMAS NMR has been investigated in application to protein samples with a variety of deuteration patterns. Samples were prepared with protons in either all hydrogen positions, only in the exchangeable sites, or in the exchangeable sites plus select methyl groups. CP dynamics, T(1) relaxation times, and (13)C line widths have been compared. Using ubiquitin as a model system, reasonable (1)H-(13)C CP transfer is observed for the extensively deuterated samples. In the absence of deuterium decoupling, the (13)C line widths observed for the deuterated samples are identical to those observed for the perprotio samples with a MAS rate of 20 kHz. Extensive deuteration has little effect on the T(1) of the exchangeable protons. On the basis of these observations, it is clear that there are no substantive compromises accompanying the use of extensive deuteration in the design of (1)H, (15)N, or (13)C solid-state NMR methods.