Crystal structure of bis[μ-N-(η2-prop-2-en-1-yl)piperidine-1-carbothioamide-κ2 S:S]bis[(thiocyanato-κN)copper(I)]

The title crystalline compound, [Cu2(NCS)2(C9H16N2)2], was obtained from the reaction of copper(I) thiocyanate (CuSCN) with (N-prop-2-en-1-yl)piperidine-1-carbothioamide as a chelating and bridging thiourea ligand in chlorobenzene. The Cu2S2 core of the dimeric molecule is situated on a crystallographic inversion centre. The copper atom is coordinated by a thiocyanate nitrogen atom, each sulfur atom of the two thiourea ligands, and the C=C double bond of the ligand in a distorted tetrahedral geometry. The dimers are linked by N—H...S hydrogen bonds, forming a network extending in two dimensions parallel to (100).

Macro Creatine Kinase (macro CK) in Clinical Practice

Creatine kinase (CK) is an important enzyme involved in energy metabolism. CK is found in the cytosol and mitochondria of various tissues, mainly those with increased energy necessities as skeletal muscle, cardiac muscle and brain, but also in visceral tissues. CK is a dimeric molecule composed of two identical or different subunits, type M - muscular and type B - brain. The combination of M and B subunits leads to formation of three isozymes: CK - MM found mainly in the skeletal muscle, CK - BB found mainly in the brain and CK - MB found mainly in the cardiac muscle, but also in small quantities in the skeletal muscle. The serum increase of different isozymes of CK is a consequence of cell disruption in various clinical situations like physical training, rhabdomyolysis, myositis, muscular dystrophy, myocardial infarction and others, CK being an important biomarker for this diseases. Macro CK is a complex of CK and immunoglobulin (macro CK type 1) or a polymer of mitochondrial CK (macro CK type 2) that induces false and persistent elevation of CK levels that could mislead the clinician. We present a review of the literature concerning the appearance and clinical significance of macro CK.

Crystal structure of the tetramethyl(phenethyl)cyclopentadienylmolybdenumtricarbonyl dimer

The structure of the dimer bis{tricarbonyl[η5-tetramethyl(phenethyl)cyclopentadienyl]molybdenum}(Mo—Mo), [Mo2(C17H21)2(CO)6], at 102 K has triclinic (P-1) symmetry. The reaction between tetramethyl(phenethyl)cyclopentadiene and molybdenum hexacarbonyl in refluxing xylenes for 18 h led to a 56% yield of the dimer as a red solid. The asymmetric unit of the structure is the tetramethyl(phenethyl)cyclopentadienylmolybdenumtricarbonyl moiety and the entire dimeric molecule is generated by inversion symmetry. The Mo—Mo bond length is 3.2773 (3) Å, a value slightly above the mean value for all [CpMo(CO)3]2 compounds listed in the CSD and slightly below the mean for [Cp*Mo(CO)3]2 complexes.

Crystal structures of the Burkholderia multivorans hopanoid transporter HpnN

Strains of the Burkholderia cepacia complex (Bcc) are Gram-negative opportunisitic bacteria that are capable of causing serious diseases, mainly in immunocompromised individuals. Bcc pathogens are intrinsically resistant to multiple antibiotics, including β-lactams, aminoglycosides, fluoroquinolones, and polymyxins. They are major pathogens in patients with cystic fibrosis (CF) and can cause severe necrotizing pneumonia, which is often fatal. Hopanoid biosynthesis is one of the major mechanisms involved in multiple antimicrobial resistance of Bcc pathogens. The hpnN gene of B. multivorans encodes an integral membrane protein of the HpnN family of transporters, which is responsible for shuttling hopanoids to the outer membrane. Here, we report crystal structures of B. multivorans HpnN, revealing a dimeric molecule with an overall butterfly shape. Each subunit of the transporter contains 12 transmembrane helices and two periplasmic loops that suggest a plausible pathway for substrate transport. Further analyses indicate that HpnN is capable of shuttling hopanoid virulence factors from the outer leaflet of the inner membrane to the periplasm. Taken together, our data suggest that the HpnN transporter is critical for multidrug resistance and cell wall remodeling in Burkholderia.

Sulfate-bridged dimeric trinuclear copper(II)–pyrazolate complex with three different terminal ligands

The reaction of CuSO4·5H2O, 4-chloropyrazole (4-Cl-pzH) and triethylamine (Et3N) in dimethylformamide (DMF) produced crystals of diaquahexakis(μ-4-chloropyrazolato-κ2N:N′)bis(N,N-dimethylformamide)di-μ3-hydroxido-bis(μ4-sulfato-κ4O:O′:O′′:O′′)hexacopper(II)N,N-dimethylformamide tetrasolvate dihydrate, [Cu3(OH)(SO4)(C3H2ClN2)3(C3H7NO)(H2O)]2·4C3H7NO·2H2O. The centrosymmetric dimeric molecule consists of two trinuclear copper–pyrazolate units bridged by two sulfate ions. The title compound provides the first example of a trinuclear copper–pyrazolate complex with three different terminal ligands on the Cu atoms, and also the first example of such complex with a strongly binding basal sulfate ion. Within each trinuclear unit, the CuIIatoms are bridged by μ-pyrazolate groups and a central μ3-OH group, and are coordinated by terminal sulfate, H2O and DMF ligands, respectively. Moreover, the sulfate O atoms coordinate at the apical position to the Cu atoms of the symmetry-related unit, providing square–pyramidal coordination geometry around each copper cation. The metal complex and solvent molecules are involved in O—H...O hydrogen bonds, leading to a two-dimensional network parallel to (10-1).

Reaction products of diorganotin(IV) oxides, R2SnO, with nitric acid. Part 2 – R = n-butyl and t-butyl

The reaction of diorganotin(IV) oxides, R2SnO with R = n-butyl and t-butyl, with nitric acid in different stoichiometric ratios resulted in the formation of different products depending on the organic groups attached to the tin atom: the diorganotin(IV) dinitrate dihydrates, n-Bu2Sn(NO3)2·2H2O (2d) and t-Bu2Sn(NO3)2·2H2O (2e), the mixed diorganotin(IV) nitrate methoxide oxide n-Bu2Sn(NO3)(n-Bu2SnOMe)O (6), and the diorganotin(IV) nitrate hydroxide hydrate t-Bu2Sn(NO3)(OH)·H2O = [t-Bu2Sn(OH)(H2O)][NO3] (7). On examination of the solubility of the primary reaction products in different solvents, the three additional compounds t-Bu2Sn(NO3)(OH)·DMSO (8), t-Bu2Sn(NO3)(OH)·THF, and 2-t-Bu2Sn(NO3)(OH)·DMF = [t-Bu2Sn(OH)dmf]2[NO3]2·[t-Bu2Sn(NO3)OH]2 (9) could be isolated. All compounds have been structurally characterized by single crystal X-ray diffraction (primary results for 7) with special attention paid to dimensionality (2d and 2c = monomeric, hydrogen bonded molecules; 6 = dimeric molecules of ladder-type structure; 7 = dimeric cation; 8 = dimeric molecule with hydrogen bonded solvent molecules; 9 = both components dimeric), tin coordination (6, 7, 8, and 9 = trigonal bipyramidal; 2d and 2e = eightfold), and nitrate bonding modes (7 and 9 = isolated, hydrogen bonded; 6, 8, and 9 (component 2) = monodentate; 2d and 2e = symmetrical bidentate), the latter one being analyzed using both Sn–O and N–O distances.

Significance of arginine radicals for sturgeon gonadotropin secondary structure and function

Significance of arginine radicals for sturgeon gonadotropin secondary structure and function Guanidine groups of arginine side chains were selectively chemically modified with 1,2-cyclohexanedione (CHD) in sturgeon (Acipenser güldenstädti Br.) gonadotropic hormone (GTH) and in its subunits. It was found that only two of the six guanidines were accessible for the reagent and each of the two modified groups was bound to an individual subunit. The results showed that both modified groups were located on the surface of the hormone dimeric molecule. CD-spectroscopy of the modified hormonal preparations did not indicate any considerable changes in their secondary structure. On the basis of the data obtained, a conclusion was made that the free guanidine groups are of exclusive importance for the hormone function at the receptor level as the bearers of the positive charge in the functionally important active sites or effector zones located on the surface of the hormone molecule. Also, it was shown that the guanidine groups played a certain role in sustaining the functionally effective spatial structure of the subunits and GTH.

Scytonemin: molecular structural studies of a key extremophilic biomarker for astrobiology

Ab initio calculations for scytonemin, an important ultraviolet (UV)-radiation protective biomolecule synthesized by extremophilic cyanobacteria in stressed terrestrial environments, are reported for the first time. Vibrational spectroscopic assignments for the previously studied Raman spectra assist in the identification of the major features in the observed data. Calculations of the electronic absorption spectra confirm the capability of this molecule to absorb in all three regions of the UV, UVA, UVB and UVC, and also illustrate the need for a dimeric species in this respect. The presence of significant steric hindrance between the two halves of the dimeric molecule about the C—C bridging bond in scytonemin forces the molecule significantly out of planarity, contrary to assumptions made in the literature; however, it appears that the monomer is capable of absorbing to only a limited extent in the UVB and UVC regions only, so conferring a special emphasis upon the need for the dimerization to remove the lower-energy UV radiation whilst still affording protection for the chlorophyll with transmission of the visible radiation required for photosynthesis. The observation of vibrational band wavenumber coincidences for the first time between the infrared and Raman spectra confirm the non-planar structural prediction from the calculations. The results of this study provide information about the protective chemical strategies of terrestrial extremophilic cyanobacteria and provide a basis for the search for molecules of this type in the astrobiological exploration of Mars.