Non empirical quantum mechanical calculations of the1H,13C,15N and17O magnetic shielding constants and of the spin-spin coupling constants in formamide,hydrated formamide and N-methylformamide

The magnetic shielding constants of the different atoms of formamide, hydrated formamide and N-methylformamide are calculated by anab initio method. For the protons of formamide the measured differences between their chemical shifts are correctly reproduced by theory, provided that the molecular geometry used as input is carefully chosen. The differences between the values of the magnetic shielding constants calculated for formamide and hydrated formamide show that intermolecular hydrogen bonding produces variations of chemical shifts for all the atoms of the molecule except the formyl proton. The calculated chemical shift variations between formamide and N-methylformamide are compared to the experimental values and discussed in relation with different hydrogen bonding possibilities of the two molecules. The calculation of the contact term of the spin-spin coupling constants of formamide and hydrated formamide shows that in most cases the measured trends are satisfactorily reproduced and that the variations of these terms upon hydration are less than 3%.     

Magnetic Orbitals and Mechanisms of Exchange I. Direct Exchange

Summary. The problem of direct exchange is examined in the simplest cases (formal coupling of two electrons initially isolated and hydrogen molecule). Then we consider the general case of a solid characterized by weak overlaps between the atomic orbitals of first-nearest neighbours so that the involved electrons are quasi-localized. We recall the physical origin of spin-orbit coupling. Its influence on direct exchange allows one to revisit Hunds rules and to express phenomenological Hamiltonians describing anisotropic couplings as well as the antisymmetrical Dzialoshinski-Moriya coupling.     

Cross-linking chemistry and biology: development of multifunctional photoaffinity probes

An efficient method of photoaffinity labeling has been developed based on rationally designed multifunctional photoprobes. Photoaffinity techniques have been used to elucidate the protein structure at the interface of biomolecules by the photochemical labeling of interacting sites. However, the identification of labeled sites within target proteins is often difficult. Novel biotinyl bioprobes bearing a diazirine photophore have contributed significantly to the rapid elucidation of ligand binding sites within proteins, thereby extending conventional photoaffinity methods. This article discusses the synthesis and applications of various photoprobes bearing a biotin, including strategies using cleavable linkages between photophores. The combination of photoaffinity methods with chip technology is also described as a novel entry to rapid affinity-based screening of inhibitors. This review focuses on a rapid and reliable photoaffinity method utilizing diazirine-based multifunctional photoprobes with numerous potential applications in functional proteomics of biomolecular interactions.     

NMR spectroscopy techniques for screening and identifying ligand binding to protein receptors

Binding events of ligands to receptors are the key for an understanding of biological processes. Gaining insight into protein-protein and protein-ligand interactions in solution has recently become possible on an atomic level by new NMR spectroscopic techniques. These experiments identify binding events either by looking at the resonance signals of the ligand or the protein. Ideally, both techniques together deliver a complete picture of ligand binding to a receptor. The approaches discussed in this review allow screening of compound libraries as well as a detailed identification of the groups involved in the binding events. Also, characterization of the binding strength and kinetics is possible, competitive binding as well as allosteric effects can be identified, and it has even been possible to identify ligand binding to intact viruses and membrane-bound proteins.     

A study of carboxylic-modified mesoporous silica in controlled delivery for drug famotidine

A series of pure silica MSU and carboxylic-modified MSU materials were prepared. The formation of mesoporous silica materials with terminal carboxylic groups on pore surface was performed by the acid-catalyzed hydrolysis of cyano to carboxylic. Then their potential applications in controlled drug delivery carriers were investigated. Drug famotidine was selected as a model molecule out of the consideration of the terminal amino groups in its molecule. The adsorption experiments show significant adsorption of famotidine on the carboxylic-modified MSU materials. And, the functionalization level of carboxylic groups has been found to be the key factor affecting the adsorption capacities of the modified MSU materials for famotidine. Subsequently, three kinds of release fluids, including simulated gastric medium, simulated intestinal medium, and simulated body fluid, were used to test the famotidine release rate from the carboxylic-modified MSU material. Obvious delayed effect has been observed for the famotidine release from the carboxylic-modified mesoporous silica material under the in vitro assays.     

原位沉析法制备磁性氧化铁羟基磷灰石/壳聚糖棒材

首先通过化学沉淀法制备磁性氧化铁羟基磷灰石(Fe3O4/HA),然后以壳聚糖(CS)为基体,利用原位沉析法将Fe3O4/HA与CS复合,制得磁性Fe3O4/HA/CS复合材料.经XRD、粒径分布和PPMS测试,结果表明了Fe3O4/HA复合物的生成.系统研究了磁性Fe3O4/HA/CS棒材力学性能的影响因素,最终确定Fe3O4与HA质量比为3∶17,磁性Fe3O4/HA与CS质量比为9∶91时,棒材的力学性能最优,弯曲强度可达到87.0 MPa,弯曲模量1.57 GPa.     

LyP-1 peptide-functionalized gold nanoprisms for SERRS imaging and tumor growth suppressing by PTT induced-hyperthermia

The gold nanoprisms (GNPs) have exhibited special plasmonic properties for biomedical applications because of their unique shapes and dimensions. Based on their optical performance, the NIR dye IR780 not only enabled the GNPs-based nanosystem as SERRS nanoparticles for Raman-encoded molecular imaging, but also enhanced the plasmonic photothermal property by laser irradiation. Meanwhile, the GNPs/IR780-Lyp-1 by introduction of tumor-homing peptide segment LyP-1, which presents high affinity to p32 protein, demonstrated the increased enrichment in tumor region and enhanced photothermal therapy efficacy.     

Transition metal complexes with thiosemicarbazide-based ligands,IV: Synthesis and molecular structure of 5-nitrosalicylaldehyde S-methylisothiosemicarbazonato-piperidine-copper(II)

Summary The reaction of warmDMF solutions of Cu(II) perchlorate, 5-nitrosalicylaldehyde S-methylisothiosemicarbazone (H₂ L) and piperidine (Pip) yielded the paramagnetic (_eff=2.19 B.M.) Cu(L)Pip complex, whereL is the dianionic form of H₂ L, formed as a result of deprotonation of the phenolic hydroxyl and NH₂ group. Crystal data of the complex are: monoclinic P2₁,a=11.902(4),b=6.765(3),c=11.343(4)Å; =112.92°,V=841.20(8)ų,M=400.9,Z=2,d ₀=1.60 gcm^–3,d _c =1.58 gcm^–3,F(000)=424. The structure was refined to a residualR=0.047. The copper(II) ion is coordinated in a square-planar arrangement by the piperidine nitrogen and the NNO set of donor atoms ofL.

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Komplexe der Übergangsmetalle mit Thiosemicarbazid-Liganden, IV. Synthese und molekulare Struktur von 5-Nitrosalicylaldehyd-S-methylisothiosemicarbazonato-piperidin-kupfer(II)

Zusammenfassung Durch die Reaktion in warmenDMF-Lösungen von Cu(II) Perchlorat, 5-Nitrosalicylaldehyd-S-methylisothiosemicarbazon (H₂ L) und Piperidin (Pip) wurde ein paramagnetischer Komplex (_eff=2.19 B.M.) Cu(L)Pip erhalten, wobeiL nach doppelter Deprotonierung (NH₂- und Phenolhydroxyl-Gruppe) als dianionische Form von H₂ L vorliegt. Die kristallographischen Daten des Komplexes sind: monokline Raumgruppe P2₁,a=11.902(4),b=6.765(3),c=11.343(4)Å, =112.92°;V=841.20ų,M=400.9,Z=2,d ₀=1.60 gcm^–3,d _c =1.58 gcm^–3,F(000)=424. Die struktur wurde bis zu einemR-Wert von 0.047 verfeinert. Die Koordination des Kupfers wird quadratisch-planar über den Piperidin-Stickstoff und die NNO-Donorhülle der Chelatliganden gebildet.

     

Determination of binding constants and stoichiometries for platinum anticancer drugs and serum transport proteins by capillary electrophoresis using the Hummel-Dreyer method

A CE method has been developed to evidence and quantitatively characterize the interaction between platinum-based antitumor drugs and human serum proteins. This method is a variant of affinity CE modified regarding both experimental setup and data treatment so as to measure the peaks (or vacancies) that correspond to the bound drug when it slowly binds to the protein. Using the formalism of the Hummel-Dreyer method and cisplatin and oxaliplatin as test compounds, a protocol for determining albumin and transferrin binding constants and stoichiometries, including (and distinguished by) 48 hours of incubation of the reaction mixture, was elaborated. Relative affinities of drugs toward different proteins in aqueous solution at physiological pH, chloride concentration, and temperature were compared in terms of overall binding constants and numbers of drug molecules attached to the protein. The results indicate that both platinum drugs bind to albumin more strongly than to transferrin, supporting the concept that the albumin fraction is a major drug supply route for chemotherapeutical needs. From a comparison with the binding parameters measured previously for cisplatin by other methods, conclusions were drawn about the validity of CE as a simple and convenient method for assaying protein-drug reactions with slow kinetics.     

U(Ⅳ)配合物UNa2(pdc)3·6H2O的合成、结构及磁性研究

合成了一种含有+4价铀的配合物UNa2(pdc)3·6H2O(H2pdc=吡啶-2,6-二羧酸), 并详细研究了其晶体结构和磁学性质. 晶体属于单斜晶系, P21/n空间群, 晶胞参数a=1.0205(2) nm, b=2.2221(4) nm, c=1.2537(3) nm, β=94.98(3)°, V=2.8323(10) nm3, Z=4. 化合物的中心铀原子为九配位, π-π相互作用和氢键使得该化合物形成了三维立体结构.