Probing proteins on functionalized silicon surfaces using matrix-assisted laser desorption/ionization mass spectrometry

Flat H-terminated Si(111) substrates modified with alkyl monolayers terminated with hydrophobic and hydrophilic functional groups were prepared using known surface functionalization methods and characterized by FTIR, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The surfaces were then used for the study of non-specific binding of proteins from complex mixtures (using standard mixture of proteins with average molecular weight approximately 6-66 kDa) by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Protein adsorption on these surfaces (following on-probe fractionation of the mixture) was found to be dependent on the nature of surface functional groups, and nature and pH of rinsing solutions used. The results obtained in this work demonstrate that simple silicon-based surface modifications can be effective for direct analysis of complex mixtures by MALDI-MS. Preliminary results obtained using similarly functionalized porous silicon substrates proved that such substrates are (due to their increased surface areas) better performing than flat silicon.     

Variable temperature STM study of Co deposition on a dodecanethiol self assembled monolayer

The present scanning tunneling microscopy study reports on the growth processes of Co vapor-deposited on a dodecanethiol (DDT) self-assembled monolayer (SAM)/Au(111). We observe strongly modified surface and depth diffusions of Co adatoms depending on the growth temperature. Co deposited at 300 K shows an extremely incomplete regime of condensation on the organic layer. Besides, Co penetrates the DDT monolayer and resides at the DDT/Au(111) interface as 2D clusters. This phenomenon takes place through defects in the SAM which are transient channels. In contrast, Co deposited at 50 K shows a complete condensation and nucleates on defects of the SAM layer as 3D islands sitting most likely on top of the DDTs. These results are of interest in the growing field of organic spintronics where the quality of the organic/ferromagnetic interface is a key issue.     

Surface reactions of 3-butenenitrile on the Si(001)-2 x 1 surface at room temperature

Using a combination of local -- scanning tunneling microscopy -- and spatially integrated, but chemically sensitive probes -- X-ray photoelectron spectroscopy and near edge X-ray absorption fine structure spectroscopy -- we have examined how 3-butenenitrile reacts with the Si(001)-2 x 1 surface at room temperature. Electron spectroscopies indicate three different nitrogen chemical bonds: a Si-C=N-Si bond, a C=C=N cumulative double bond, and a CN moiety datively bonded to a silicon atom. All molecular imprints detected by scanning tunneling microscopy (STM) involve two adjacent silicon dimers in the same row. The three geometries we propose -- a double di-sigma bonding via the CN and the C=C, a cumulative double bond formation associated with alphaC-H bond dissociation, and a di-sigma vinyl bonding plus a CN datively bonded to a silicon atom -- are all compatible with electron spectroscopies and data. Real-time Auger yield kinetic measurements show that the double di-sigma bonding geometry is unstable when exposed to a continuous flux of 3-butenenitrile molecules, as the Si-C=N-Si unit transforms into a CN moiety. A model is proposed to explain this observation.     

Design, synthesis, and cytotoxic activity of Michael acceptors and enol esters in the benzo[b]acronycine series

A series of 2-acyl-6-methoxy-3,3,14-trimethyl-3,14-dihydro-7H-benzo[b]pyrano[3,2-h]acridin-7-ones (4-6) was prepared by treatment of 6-methoxy-3,3,14-trimethyl-3,14-dihydro-7H-benzo[b]pyrano[3,2-h]acridin-7-one (3) with an excess of an appropriate acyl chloride in the presence of aluminum chloride. Treatment of (+/-)-cis-1-hydroxy-2-acyloxy-6-methoxy-3,3,14-trimethyl-1,2,3,14-tetrahydro-7H-benzo[b]pyrano[3,2-h]acridin-7-ones (9, 10) or (+/-)-cis-1,2-diacyloxy-6-methoxy-3,3,14-trimethyl-1,2,3,14-tetrahydro-7H-benzo[b]pyrano[3,2-h]acridin-7-ones (2, 11) with hydrochloric acid gave the corresponding 2-acyloxy-6-methoxy-3,3,14-trimethyl-3,14-dihydro-7H-benzo[b]pyrano[3,2-h]acridin-7-ones, exemplified by acetate 7 and butyrate 8. None of the Michael acceptors 4-6 showed significant antiproliferative activity. Enol esters 7 and 8 were markedly cytotoxic toward L1210 leukemia cells, with IC50 values within the same range of magnitude as (+/-)-cis-1,2-diacetoxy-6-methoxy-3,3,14-trimethyl-1,2,3,14-tetrahydro-7H-benzo[b]pyrano[3,2-h]acridin-7-one (S23906-1), currently under phase I clinical trials. In contrast with S23906-1, enol esters 7 and 8 were not reactive toward purified DNA.     

Binuclear manganese compounds of potential biological significance. 1. Syntheses and structural,magnetic, and electrochemical properties of dimanganese(II) and -(II,III) complexes of a bridging unsymmetrical phenolate ligand

Reactions of the unsymmetrical phenol ligand 2-(bis(2-pyridylmethyl)aminomethyl)-6-((2-pyridylmethyl)(benzyl)aminomethyl)-4-methylphenol with Mn(OAc)(2).4H(2)O or Mn(H(2)O)(6)(ClO(4))(2) in the presence of NaOBz affords the dimanganese(II) complexes 1(CH(3)OH), [Mn(2)(L)(OAc)(2)(CH(3)OH)](ClO(4)), and 2(H(2)O), [Mn(2)(L)(OBz)(2)(H(2)O)](ClO(4)), respectively. On the other hand, reaction of the ligand with hydrated manganese(III) acetate furnishes the mixed-valent derivative 3(H(2)O), [Mn(2)(L)(OAc)(2)(H(2)O)](ClO(4))( 2). The three complexes have been characterized by X-ray crystallography. 1(CH(3)OH) crystallizes in the monoclinic system, space group P2(1)/c, with a = 10.9215(6) A, b = 20.2318(12) A, c = 19.1354(12) A, alpha = 90 degrees, beta = 97.5310(10) degrees, gamma = 90 degrees, V = 4191.7 A(3), and Z = 4. 2(H(2)O) crystallizes in the monoclinic system, space group P2(1)/n, with a = 10.9215(6) A, b = 20.2318(12) A, c = 19.1354(12) A, alpha = 90 degrees, beta = 97.5310(10) degrees, gamma = 90 degrees, V = 4191.7 A(3), and Z = 4. 3(H(2)O) crystallizes in the monoclinic system, space group P2(1)/c, with a = 11.144(6) A, b = 18.737(10) A, c = 23.949(13) A, alpha = 90 degrees, beta = 95.910(10) degrees, gamma = 90 degrees, V = 4974(5) A(3), and Z = 4. Magnetic measurements revealed that the three compounds exhibit very similar magnetic exchange interactions -J = 4.3(3) cm(-)(1). They were used to establish tentative magneto-structural correlations which show that for the dimanganese(II) complexes -J decreases when the Mn-O(phenoxo) distance increases as expected from orbital overlap considerations. For the dimanganese(II,III) complexes, crystallographic results show that the Mn(II)-O(phenoxo) and Mn(III)-O(phenoxo) bond lengths are inversely correlated. An interesting magneto-structural correlation is found between -J and the difference between these bond lengths, delta(Mn)(-)(O) = d(Mn)()II(-)(O) - d(Mn)()III(-)(O): the smaller this difference, the larger -J. Electrochemical studies show that the mixed-valence state is favored in 1-3 by ca. 100 mV with respect to analogous complexes of symmetrical ligands, owing to the asymmetry of the electron density as found in the analogous diiron complexes.     

Water sorption in hybrid silica gels containing colloidal nontronite

Hybrid silica gels (HSGs) were prepared according to an acid-catalyzed sol–gel method using tetraethoxysilane (TEOS) as silica precursors and colloidal suspension of nontronite clay mineral. The silica surfaces were hydrophilic in relation to silanol groups and it was of interest to increase hydrophobicity by substituting silanol by methylated groups through addition of methyltrimethoxysilane (MTMS) in a molar ratio TEOS: MTMS equaled to 1:0.4. The aim of the present paper was to predict effects of water content in soil on HSG hydration by characterizing HSG water desorption and sorption with dynamic vapor sorption device. From desorption kinetics, TEOS HSGs showed higher ability to water surface evaporation and diffusion compared to the TEOS–MTMS HSGs. After complete dehydration, water sorption isotherms Type II were obtained for HSGs. Isotherms were fitted with Brunauer-Emmett-Tellet (BET) and Guggenheim, Andersen, de Boer (GAB) models. The higher monolayer values of water adsorbed for HSGs containing nontronite suggested a major influence of clay minerals on overall hydration. However, the water binding energy depended upon the nature of silica matrix indicating weaker bonds with methylated groups at solid surface in MTMS–TEOS HSGs. Apparent water sorption diffusivities, D_app were calculated according to Fick’s diffusion model. Maximal D_app values were obtained in the range 0.2??.3 a_w after which the D_app decreased in relation with capillary condensation.     

Electropolymerization of [Ru(bpy)(CO)2Cl2] (bpy=2,2′-bipyridine: a revisited trans versus cis(Cl) isomeric influence study

The mono-bipyridine bis carbonyl complex [Ru(bpy)(CO)₂Cl₂] exists in two stereoisomeric forms having a trans(Cl)/cis(CO) (1) and cis(Cl)/cis(CO) (2) configuration. In previous work we reported that only the trans(Cl)/cis(CO) isomer 1 leads by a two-electron reduction to the formation of [Ru(bpy)(CO)₂]_n polymeric film on an electrode surface. This initial statement was overstated, as both isomers allowed the build up of polymers. A detailed comparison of the electropolymerization of both isomers is reported here, as well as the reduction into dimers of parent stereoisomer [Ru(bpy)(CO)₂(C(O)OMe)Cl] complexes 3 and 4 obtained as side products during the synthesis of 1 and 2.     

Stable isotope ratio measurements of royal jelly samples for controlling production procedures: impact of sugar feeding

The carbon and nitrogen stable ratios of royal jelly (RJ) samples from various origins are determined using an elemental analyser linked online to an isotope ratio mass spectrometer to evaluate authenticity and adulteration. The (13)C/(12)C and (15)N/(14)N stable isotope ratios are measured in more than 500 RJs (domestic, imported and derived from feeding experiments) in order to obtain isotopic measurements that take into account seasonal, botanical and geographical effects. Authenticity intervals are established for traditional beekeeping practices, without feeding, in the range -22.48 to -27.90‰ for δ(13)C. For these samples, the δ(15)N values range from -1.58 to 7.98‰, depending on the plant sources of pollen and nectar. The δ(13)C values of the commercial samples vary from -18.54 to -26.58‰. High δ(13)C values are typical of sugar cane or corn syrups which have distinctive isotopic (13)C signatures because both plants use the C4 photosynthetic cycle, in contrast to most RJs which are derived from C3 plants. These differences in the (13)C-isotopic composition allow the detection of the addition of such sugars. RJs from traditional sources and from industrial production by sugar feeding are thus successfully distinguished.     

Simple complementary liquid chromatography and mass spectrometry approaches for the characterization of triacylglycerols in Pinus koraiensis seed oil

A new simple strategy to identify triacylglycerols (TAGs) in oils and fats was performed using on line coupling of non aqueous reversed phase chromatography-electrospray ionization-mass spectrometry (NARP-LC-ESI-MS(2)) with silver nitrate (AgNO(3)) as post-column additive, and chromatographic data (partition number information and both the graphs of log k vs. number of double bond (DBN) and carbon number (CN)). NARP liquid chromatography permitted to separate TAGs composed of Δ5 and Δ9 but not from Δ11 double bond location on alkyl chain of fatty acid residues. Silver cationization improved the sensitivity by a factor one hundred. MS(2) information gave unambiguously the nature of three fatty acid residues bonded to glyceryl backbone of TAGs while log k against DBN and CN curves discriminated between the same molecular mass TAG isomers (whose constitutive fatty acid residues are double bond position and configuration isomers). Combination of structural information given by MS with chromatographic retention laws led to the development of a general methodology for determination of the structure of TAGs in lipids. This methodology was applied to Pinus koraiensis seed oil for which some uncommon TAGs are present. It permitted the identification of 58 TAGs in this oil. The experimental proof of 29 uncommon TAGs as component of this oil is demonstrated. Among them 26 were minor constituents.     

Synthesis and characterization of nanoapatites organofunctionalized with aminotriphosphonate agents

Organofunctionalized apatite nanoparticles were prepared using a one step process involving dissolution/precipitation of natural phosphate rock and covalent grafting of nitrilotris(methylene)triphosphonate (NTP). The synthesized materials were characterized by Brunauer–Emmett–Teller (BET) surface measurement, thermogravimetry, inductively coupled plasma emission spectroscopy (ICP–ES), elemental analysis, multinuclear solid state cross-polarization/magic angle spinning (CP/MAS) and single-pulse NMR spectroscopy, transmission electron microscopy (TEM) and energy dispersive X-ray analysis (EDXA). After grafting BET measurements yielded particle specific surface areas ranging from 88 to 193 m² g^?1 depending on the grafted phosphonate. The results show that the surfaces of the nanoapatite particles can be covered with functional groups bound through a variable number of R–P–O–Ca bonds to render them organoapatites.