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A systematic study is reported on the effect of linker size and its chemical composition toward ligand binding to a surface-immobilized aptamer, measured using surface plasmon resonance. The results, using thrombin as the model system, showed that as the number of thymidine (T) units in the linker increases from 0 to 20 in four separate increments ([T.sub.0], [T.sub.5], [T.sub.10], [T.sub.20]), the surface density of the aptamer decreased linearly from approximately 25 to 12 pmol x [cm.sup.-2]. The decrease in aptamer surface density occurred due to the increased size of the linker molecules. In addition, thrombin binding capacity was shown to increase as the linker length increased from 0 to 5 thymidine nucleotides and then decreased as the number of thymidine residues increased to 20 due to a balance between two different effects. The initial increase was due to increased access of thrombin to the aptamer as the aptamer was moved away from the surface. For linkers greater in length than [T.sub.5], the overall decrease in binding capacity was primarily due to a decrease in the surface density. Incorporation of a hexa(ethylene glycol) moiety into the linker did not affect the surface density but increased the amount of thrombin bound. In addition, the attachment of the linker at the 3'- versus the 5'-end of the aptamer resulted in increased aptamer surface density. However, monolayers formed with equal surface densities showed similar amounts of thrombin binding irrespective of the point of attachment.

Electronic structures at the Si/Si[O.sub.2]/molecule interfaces are studied by using Kelvin probe techniques and are compared to theoretical values derived by the Helmholtz equation. The studies have shown an increase in the electronic effects on the Si substrate by increasing surface chromophoric coverage and a major consequence of depolarization is detected while comparing the experimental and calculated values.

The rectification of electrical current is observed in a Langmuir-Schaefer monolayer of fullerene-bis[ethylthio-tetrakis(3,4-dibutyl-2-thiophene-5-ethenyl)-5-bromo-3,4-dibutyl-2-thiophene] malonate, Au electrodes at room temperature and also between Pb and Al electrodes at 4.2 K. The second derivative of the current with respect to voltage spectrum has shown intramolecular vibrations and two antisymmetric broad bands due to resonant electron tunneling between Fermi levels of the electrodes and the lowest unoccupied molecular orbital of the molecule.

The surface-initiated polymerization of a hydrophilic polymer, hyperbranched polyglycidol (HPG) from minority surface sites embedded in a hydrophobic matrix demonstrate that a covalently tethered polymer molecule could spontaneously break away (desorb) from the surface when polymer/surface interaction is sufficiently unfavorable.

The structure and property odd-even effects of various organic monolayers self-assembled on solid surfaces are described.

The self-assembled monolayers (SAMs) on the gold surface are analyzed for their structures based on the electrostatic interactions influencing the degree of disorder in carboxyl-terminated SAMs. The findings suggest that the presence of dipole moments influences the structure of the corresponding alkanethiol monolayer.

Infrared reflection absorption spectroscopy (IRRAS) and surface plasmon resonance (SPR) techniques are used to investigate human serum albumin (HSA) binding to binary monolayers of zwitterionic dipalmitoylphosphatidylcholine (DPPC) and cationic diactadecyldimethylammonium bromide (DOMA). The two components in the monolayers deliver through lateral reorganization to form multiple interaction sites favorable for protein binding.

The [super 1]H NMR investigation is employed to measure the thickness of the pre-molten surface layer formed at the interface of octamethylcyclotetrasiloxane (OMCTS) to the matrix in controlled pore glasses with different pore diameters. The study reveals that the surface layer thickness highly depends on the curvature of the pore wall and the solid-liquid interface, as OMCTS itself is a weakly polar molecule with close to spherical shape.

The vibrational sum frequency generation (SFG) spectroscopy is employed to investigate and explore the phase transitions of several phospholipid monolayers containing poly(ethylene oxide) lipids at the air-water interface. The results indicate that the mixed monolayers exist in pancake, mushroom or the brush state, wherein the mushroom-brush transition accompanies the conversion of the alkyl group from an irregular structure to the all-trans structure.

Various researches are employed to analyze the role of various indifferent electrolytes on the concentration polarization, potential distributions and the monolayer charge of the process of Langmuir monolayer deposition onto a substrate surface. The results show that the indifference electrolytes lead to an increase in the deposition rate, which further increases the monolayer ionization and charge that is not normally observed otherwise.

The effects of bridge ions, DNA species and developing temperature on the configuration of DNA monolayers are investigated by using atomic force microscopy (AFM). The results have indicated that the appropriate interactions between divalent cations and DNA or mica surface are important for the formation of flat-lying DNA monolayers.

Bile acid epimers and side-chain homologues are present in the human colon. To test whether such bile acids possess secretory activity, cultured T84 colonic epithelial cells were used to quantify the secretory properties of synthetic epimers and homologues of deoxycholic acid (DCA) and chenodeoxycholic acid (CDCA). In our study, chloride secretion was measured as changes in short-circuit current ([DELTA][I.sub.SC], in [microLA/[cm.sup.2]) with the use of voltage-clamped monolayers of T84 cells mounted in Ussing chambers. Bile acids were added at 0.5 mM, a concentration that did not alter transepithelial resistance. Data were expressed as peak [DELTA][I.sub.SC] (means [+ or -] SD). When added bilaterally, DCA stimulated a [DELTA][I.sub.SC] response of 15.7 [+ or -] 12.5 [micro]A/[cm.sup.2]. The 12[beta]-OH epimer of DCA was less potent ([DELTA][I.sub.SC] = 8.0 [+ or -] 1.7 [micro]A/[cm.sup.2]), whereas its 3[beta]-OH epimer had no effect. CDCA stimulated secretion ([DELTA][I.sub.SC] = 8.2 [+ or -] 5.5 [micro]A/[cm.sup.2]), whereas both its 7[beta]-OH and 3[beta]-OH epimers were inactive, as was lithocholic acid. HomoDCA (1 additional side-chain carbon) was active ([DELTA][I.sub.SC] = 7.8 [+ or -] 4.8 [micro]A/[cm.sup.2]), whereas norDCA (1 fewer carbon) and dinorDCA (2 fewer carbons) were not. Taurine conjugates of DCA and CDCA stimulated secretion (Alsc = 12.3 [+ or -] 7.5 and 8.8 [+ or -] 4.8 [micro]A/[cm.sup.2], respectively) from the basolateral side but not the apical side. Uptake of taurine conjugates from the basolateral but not the apical side was shown by mass spectrometry. These studies indicate marked structural specificity for bile acid-induced chloride secretion and show that modification of bile acid structure by colonic bacteria modulates the secretory properties of these endogenous secretagogues. bile acid homologues; conjugated bile acids; bile acid physiology

The interfacial property and current transport in the metal/Hf[O.sub.2]/silicon structure are studied. An interfacial layer of Hf-silicate was formed between 700 degree Celsius-annealed Hf[O.sub.2] and Si.

The density functional theory (DFT) ab initio calculation of Fe-silicon hybrid redox potentials is reported. It is suggested that the hydrosilylation activated by visible light proceeds through a mechanism, which is not yet described, thus indicating that saturations are preserved during the addition.

The effectivities of solution-processable self-assembled nanodielectrics (SANDs) and cross-linked polymer blends (CPBs) organic nanodielectrics are investigated by using Maxwell-Garnett effective medium approximation (EMA) models. The results have shown that greater capacitances can be achieved with cross-linked composites than with layered composites when all parameters are equal.

The results of experimental measurements of the viscoelastic behavior of the fatty acid 2-hydroxytetracosanoic acid (2-OH TCA) and X-ray measurements of the monolayer structure are reported. Two interesting behaviors, phase coexistence between the [L.sub.2h] and L2' phases over a large pressure range and a peak in the viscosity and elastic modulus of the material as a function of pressure are observed.

The friction and triboelectrification between both similar and dissimilar molecularly smooth hexadecanethiol-coated metal surfaces on mica substrates were simultaneously measured using a modified surface forces apparatus. Results indicate that frictional dissipation induces electron-hole formation and charge transfer between two shearing surfaces due to molecular-level roughness and defects and local dielectric constant changes, giving rise to the observed tribocurrents.

The interaction of the glycoalkaloid tomatine with monolayers of dimyristoylphosphatidylcholine (DMPC) and cholesterol, as well as other selected sterols, were studied using surface pressure measurements at constant area and Brewster angle microscopy. It is found that the interaction of tomatine with cholesterol-containing monolayer results in a surface pressure increase accompanied by the appearance of a mottled texture.

The bipolar amphiphile 22-methoxydocosan-1-ol (H3C-O-(CH2)22-OH, MDO) and the monopolar amphiphle dicosyl methyl ether (H3C-(CH2)21-O-CH3, DME) were selectively synthesized for the first time as model compounds to elaborate the effect of a second polar group on the monolayer behavior by comparison with the corresponding alcohol docosan-1-ol (H3C-[CH2).sub.21-OH, DO). GIXD data show that the monolayers exhibit the phase sequence L2'-S at lower temperature and L2'-LS at higher temperature.

A study demonstrates that the two-dimensional surface shear viscosity, [eta], of fatty acid monolayers of different chain lengths, measured using a simple magnetic needle viscometer, strongly correlates with the molecular organization in condensed phases and the absolute temperature. It is found that [eta] could increase by orders of magnitude at phase boundaries associated with tilted to untilted molecular order, providing the underlying order is semicrystalline.

The results of fully atomistic molecular dynamics (MD) simulations of a series of Gemini surfactants, C5H25-[alpha],[omega]-bis([C12H25N.sup.+](CH3)2[Cl.sup.-]), at the air/water interface with s=3,4,6,12,14, and 16, at values of the initial surface area per surfactant [A.sub.s]= 70 [angstrom.sup.2], 77 [angstrom.sup.2], 95 [angstrom.sup.2], 151 [angstrom.sup.2], 151 [angstrom.sup.2], 133 [angstrom.sup.2], and 103 [angstrom.sup.2], respectively, are reported. The MD simulations are found to confirm the bending of the spacer toward the hydrophobic chains as the spacer length is increased and the spacer becomes more hydrophobic.

The local collapse of a two-dimensional Langmuir monolayer locally heated by an infrared laser is reported. Results predict that local collapse could be induced if the collapse pressure of the monolayer decreases faster with temperature than with the surface tension of the pure air/water interface.

The adsorption of neuropeptide Y (NPY) with air-water interfaces and with phospholipid monolayers on water subphases and on physiological buffer is investigated. Surface pressure versus molecular area solutions of the peptide at water surfaces depend on the concentration of the spreading solutions.

A study demonstrates that the lipid tubules of 1,2-bis(tricosa-10,12-diynoyl)-sn-glycero-3-phosphocholine could be bent into a looplike shape by shrinking contact line of droplets on self-assembled monolayers (SAMs) of 1-dodecanethiol. An examination of the radial deformation of the lipid tubules on SAMS under applied load using atomic force microscope revealed that the stiffness of the tubules in the radical direction increased when the number of the lipid bilayers in the tubule was increased.

The binary films containing dioleoyl phosphatidylcholine-dipalmitoyl phosphatidylcholine (DPPC) mixtures between 10 and 100% DPPC were studied in order to determine the way coexistence of liquid-expanded (LE) and tilted-condensed (TC) phases in phospholipid monolayers affects collapse from the air/water interface. Results reveal that although coexisting solid and fluid phases collapse to extents that are independent, the kinetics of collapse, corrected for differences in LE area, depend on the distribution of the two phases.

The capacitance of monolayer-protected gold nanoclusters (MPCs), [C.sub.PMC], in solution was theoretically reconsidered from an electrostatic viewpoint, in which an MPC was considered as an isolated charged sphere within two dielectric layers, the intrinsic coating monolayer, and the bulk solvent. The model predicted that the bulk solvent provides an important contribution to [C.sub.MPC] and influences the redox properties of MPCs.

[C.sub.60] nanostructures with long-range order and uniform size are prepared using a vicinal Au(11 12 12) surface, naturally patterned into a rectangular superlattice as a template. A two-dimensional long-range ordered superlattice of molecular nanochains is achieved at room temperature and at a coverage of 0.1 monolayer, which perfectly replicates the periodicity of the template surface.

The effect of interfacial water on the structural and electronic properties of pentacene monolayer deposited on Si[O.sub.2] is investigated. The combined structural and electronic results have suggested that the sensitivity to environmental conditions is not caused by a change in the amount of moisture at the interface, but it is predominantly related to condensed moisture at the free surface or at exposed grain boundaries in the film.

A study on the adsorption and growth of a C60 monolayer on a TiO2(110)-1 x 2-cross-link structure is conducted by scanning tunneling microscopy (STM). By applying a high negative bias voltage (-3.5 V) to an STM tip on the C60 monolayer, C60 oligomers are formed accompanied with the contraction of C60-C60 distance along the C60 row and bright contrast in the STM image.

A series of amphiphilic lipopeptides (ALPs), consisting of an alternating hydrophilic and hydrophobic amino acid residue sequence coupled to a phospholipids tail, was designed to form supramolecular assemblies composed of beta-sheet monolayers decorated by lipid tails at the air-water interface. In situ grazing-incidence X-ray diffraction (GIXD) revealed that lipopeptides six to eight amino acids in length form a new type of 2-dimensional (2D) self-organized monolayers that exhibit beta-sheet ribbons segregated by lipid tails.

A study investigates self-assembled monolayers (SAMs) of two omega-(4'methylbiphenyl-4-yl)alkanethiois { C[H.sub.3][(C6H4).sub.2]-[(C[H.sub.2]).sub.n]SH, BPn, n = 4,6 } on Au(111) substrates, prepared from solution at room temperature and subsequently annealed at temperatures up to 493 K under a nitrogen atmosphere. Results show that, in striking contrast to BPn SAMs with n = odd, for which only one phase is observed, the even-numbered BPn SAMs exhibit polymorphism.

The structural characteristics and adsorption behavior of 4,4'-thiobenzenethiol (TBBT) self-assembled monolayers (SAMs) on Au is investigated by surface enhanced Raman scattering (SERS), electrochemical cyclic voltammetry (CV), ac impedance spectroscopy (EIS), and atomic force microscopy (AFM). A scanning electron microscopic image of Ag nanoparticles on TBBT/Au and the Raman spectrum of TBBT in smooth macroscopic Au/TBBT SAMs/Ag nanoparticle sandwich structure indicate that metal nanoparticles could be adsorbed on TBBT SAMs effectively through covalent linkage.

Electroactive tetrathaifulvalene (TTF)-containing alkanethiol self-assembled monolayers (SAMs) are designed and synthesized to elucidate the relationship between electrochemical responses and film structures. Results reveal that TTF-based SAMs exhibited collective electrochemical responses induced by dynamic structural changes, depending on the degree of freedom for the component molecules in the SAMs.

Self-assembled monolayers (SAMs) prepared from fullerene derivatives of thiols/thiol esters/disulfides are analyzed in detail and the complications due to multilayer formations and head-to-tail assemblies are revealed. Several fullerene derivatives based on thiols, thiol acetates and disulfides are designed and synthesized to address the characterization requirements and these are described and delineated.

An investigation of the interaction between chlorpromazine (CPZ) and monolayers of 1,2-dipalmitoyl-sn-3-glycerophosphatidylcholine (DPPC) and 1,2-dipalmitoyl-sn-3-glycero[phospho-rac-(1-glycerol)] (DPPG), both at the air/water interface and in transferred Langmuir-Blodgett films is presented. The IR and compressibility results demonstrate that the effect from CPZ could not be correlated with temperature changes in the subphase for pure monolayers, in contrast to models proposed by other authors.

The growth and magnetic properties of magnetic monolayers grown on a Pt(997) vicinal single crystal surface at room temperature is investigated. The magnetic easy axis of the atomic layers is perpendicular to the surface due to strong surface anisotropy.

This paper describes a new and simple microarray platform for presenting multiple nonderivatized oligosaccharides to protein targets, with utility for mapping carbohydrate--protein recognition events. The approach is based on the creation of a hydrazide-derivatized, self-assembled monolayer on a gold surface in a single or two-step procedure, for efficient and selectively oriented anchoring of oligosaccharide probes via their reducing ends, with detection using fluorescence detection of bound proteins. The biggest hurdles in employing gold-based substrate for fluorescence-based microarray detection include fluorescence quenching and nonspecific surface adsorption of proteins. We found that the quenching effect could be minimized by introducing a [omega]-thiolated fatty acid (C16) self-assembled monolayer between the gold surface and hydrazide groups, followed by detection involving three successive binding protein layers covering the gold surface. In addition, an effective blocking scheme involving poly(ethylene glycol) aldehyde and bovine serum albumin was employed to reduce nonspecific protein adsorption to the chip surface. As proof of principle, we demonstrate here that sulfated oligosaccharide probes from heparin can be effectively and covalently attached without prior derivatization onto the hydrazide-modified, self-assembled monolayer on gold-coated slide surfaces in a microarray format. This platform is used to assess binding of specific heparin-binding protein targets at very high sensitivity, and we also demonstrate that the approach can be extended to nonsulfated sugars. Direct attachment of nonderivatized sugar probes on the chip is advantageous since it avoids the need for laborious prederivatization and cleanup steps. This versatile fluorescence microarray platform provides a facile approach for interrogating multiple carbohydrate--protein interactions in a high-throughput manner and has potential as a common gold surface platform for other diverse interrogations by MALDI-MS, surface plasmon resonance, and quartz crystal microbalances.

A 16-fold metal-enhanced fluorescence (MEF) from well organized and closely packed long-chain nitrobenzoxadiazole (NBD-C16 and NBD-C18) probes on silver island films (SIFs) deposited with the use of the Langmuir-Blodgett technique is reported. The results reveal that the increase in MEF efficiency is justified based on the cooperative effects of the modulations in electronic density of the surface plasmon absorption band of SIFs and defined probe orientation that might lead to preferential excitation.

The influence of subphase characteristics on the conformation and lateral and lateral orientation of the hydrophobic polypeptide poly-L-leucine at the air-water interface with the surface film balance technique as well as with Brewster angle microscopy (BAM) is investigated. Kinetics studies of monolayer relaxation strongly suggest that the end-group effects influence the thermodynamic, as well as the kinetic, properties of peptide monolayers.

Geometric modelling techniques are used to map the potential energies of packing for self-assembled alkyland phenyl-backboned monolayers across a range of intermolecular separations. Natural packing distances of 4.2-4.4 Angstrom produce less stable, more isotropic monolayers because of repulsive interchain contacts. Optimizations at unnatural surface densities found thin films of lower energy and higher symmetry existed at increased chain-chain separations. Head-group bonding is therefore identified as a force for controlling monolayer order. Analysis of the natural monolayer structures on a silicon dioxide surface determined the favourable head-group structures, and allowed the topochemical polymerization of p-bis(butadiynyl)benzene monolayers to be rationalized. Key words: self-assembled monolayers, molecular modelling studies, repeating symmetry units, thin-film order, topochemical polymerization.

A periodic slab model consisting of five layers of Ag covered on both side by NiO monolayers is adopted to stimulate the properties of ultrathin layers of nickel oxide epitaxially grown on silver (001). The presence of the metallic substrate is found to influence the structural, electronic, and magnetic properties of the overlayer but only to a limited extent.

The monolayers of hexadecylquinolinium tricyanoquinnodimethanide [C(sub 16)H(sub 33)Q(super +)-3CNQ(super -)] on gold surfaces and the structure by surface plasmon resonance (SPR) are prepared. The surface spectroscopic measurements indicate that the molecules in the monolayer are aligned such that the terminal cyano groups are absorbed on gold surface, and that the aliphatic chain is away from the surface.

A laser-induced thermocapillary pump is used to investigate flow-controlled fingering of the liquid expanded/liquid condensed phase boundary in a 2-d insoluble monolayer. It is found that the transient growth as well as the stationary patterns point toward a flow controlled fingering instability, an intrinsic mechanism, and does not depend on the fluorescence label concentration.

The synthesis of isolipoic acid, a symmetrical and achiral isomer of [alpha]-lipoic acid, through a new route and its functionalization with ferrocenyl groups for redox-active self-assembled monolayer (SAM) formation on gold electrodes is described.

A controllable cross-linking within a self-assembled monolayer is used as a tool for examining the intermolecular coupling between adjacent organic molecules. The results are based on macroscopic electrical experiments with self-assembled hexyltrichlorosilane (HTS) having different degrees of Si-O-Si intermolecular bonds in a planar nanogap junction.

The article presents a new series of intermetallics, which can be used as electrocatalysts for the Pt monolayer [O.sub.2] reduction. The compounds are shown to be highly advantageous, as they lead to a significant enhancement of activity, stability and other properties of the monolayers.

Several studies are conducted to explain the molecular rectification taking place in the several different metal-self assembled monolayer (SAM)-metal oxide-metal junctions. The abilities of the different SAMs with and without the head groups to conduct charge are also discussed.