Biomedical subjects

Michael Grunze

Publications and source records attributed to Michael Grunze.

At least 19 recordsLinked to original sources

PubMed2006

Polarized infrared microspectroscopy of single spruce fibers: hydrogen bonding in wood polymers.

We studied wood polymers in their native composite structure using mechanically isolated single spruce (Picea abies [L.] Karst.) fibers. Dichroic infrared spectra of fibers placed in a custom-built microfluidic cuvette were acquired in air, in liquid (heavy) water, and in liquid dimethylacetamide using a novel combination of synchrotron-based Fourier transform infrared microspectroscopy with polarization modulation. Differences were observed in the O-H stretching frequency region of the spruce spectra upon changing the ambient conditions. Analysis of these spectral variations provides information on hydrogen bonding, orientation, and accessibility of structural units of the wood polymers in the spruce cell walls. Our in situ approach contributes to a further understanding of the structural details of wood polymers in their native setting.

Cellulose↗

PubMed2006

Water as a lubricant for graphite: a computer simulation study.

The phase state and shear behavior of water confined between parallel graphite sheets are studied using the grand canonical Monte Carlo technique and TIP4P model for water. In describing the water-graphite interaction, two orientation-dependent potentials are tried. Both potentials are fitted to many-body polarizable model predictions for the binding energy and the equilibrium conformation of the water-graphite complex [K. Karapetian and K. D. Jordan in Water in Confining Geometries, edited by V. Buch and J. P. Devlin (Springer, Berlin, 2003), pp. 139-150]. Based on the simulation results, the property of water to serve as a lubricant between the rubbing surfaces of graphitic particles is associated, first, with the capillary condensation of water occurring in graphitic pores of monolayer width and, second, with the fact that the water monolayer compressed between graphite particles retains a liquidlike structure and offers only slight resistance to shear.

Journal Article↗

PubMed2006

Oxygen K-edge X-ray absorption fine structure studies of vacuum-deposited ice films.

Multilayer ice films deposited on polycrystalline Au(111) substrates at 90 and 153 K under ultra-high-vacuum conditions are studied using O K-edge X-ray absorption fine structure spectroscopy in the surface-sensitive partial electron yield mode. Both near-edge and extended oscillatory fine structures are analyzed in combination with the theoretical real-space full-multiple-scattering simulations based on the FEFF8 code. The experimental data consistently indicate that the local structure of the near-surface regions in ice films at both substrate temperatures resembles that of high-density crystalline modifications of ice (e.g., ice II, ice III, or high-density amorphous ice). In addition, the ice films deposited at 153 K most probably contain a minor fraction of low-density cubic ice (I(c) phase).

Journal Article↗

PubMed2006

Scanning transmission X-ray microscopic analysis of purified melanosomes of the mouse iris.

Melanosomes are specialized intracellular membrane bound organelles that produce and store melanin pigment. The composition of melanin and distribution of melanosomes determine the color of many mammalian tissues, including the hair, skin, and iris. However, the presence of melanosomes within a tissue carries potentially detrimental risks related to the cytotoxic indole-quinone intermediates produced during melanin synthesis. In order to study melanosomal molecules, including melanin and melanin-related intermediates, we have refined methods allowing spectromicroscopic analysis of purified melanosomes using scanning transmission X-ray microscopy. Here, we present for the first time absorption data for melanosomes at the carbon absorption edge ranging from 284 to 290 eV. High-resolution images of melanosomes at discrete energies demonstrate that fully melanized mature melanosomes are internally non-homogeneous, suggesting the presence of an organized internal sub-structure. Spectra of purified melanosomes are complex, partially described by a predominating absorption band at 288.4 eV with additional contributions from several minor bands. Differences in these spectra were detectable between samples from two strains of inbred mice known to harbor genetically determined melanosomal differences, DBA/2J and C57BL/6J, and are likely to represent signatures arising from biologically relevant and tractable phenomena.

Absorption↗

PubMed2006

Solid-state near-edge X-ray absorption fine structure spectra of glycine in various charge states.

The experimental solid-state near-edge X-ray absorption fine structure spectra for a series of glycine-related samples including alpha-glycine, beta-glycine, glycinium chloride, glycinium trifluoroacetate, and sodium glycinate at the C, N, and O K-edges measured under identical conditions are reported and compared. An assignment of spectral features for alpha-glycine is proposed on the basis of extended theoretical simulations of polarization-dependent spectra performed within the real-space multiple-scattering formalism explicitly taking into account the intermolecular environment of a glycine molecule in a crystal.

Adsorption↗

PubMed2006

Self-assembled molecular pattern by chemical lithography and interfacial chemical reactions.

The fabrication of lipid-modified molecular patterns by Chemical Lithography combined with interfacial chemical reactions is reported. In this method, self-assembled monolayers (SAMs) of 4'-nitro-1,1'-biphenyl-4-thiol (NBT) were structured by Chemical Lithography which produced cross-linked 4'-amino-1,1'-biphenyl-4-thiol (cABT) monolayers within a nitro-terminated (NBT) matrix. The terminal amino groups in the cABT monolayer were diazotized to create diazo cations, and the lipid monolayer with negative charge was assembled on the diazo regions by electrostatic attraction. Under the exposure of UV light, the photoreaction occurs. The diazonium groups interacting with the lipid headgroups via electrostatic attraction decompose and release N2 which leads to the lipid monolayer covalently attaching to the cABT region. The presence of phosphorus in X-ray photoelectron spectra (XPS) reveals the binding of the phospholipid layer to the cABT surface. Atomic force microscopy (AFM) images display that lipid-modified molecular patterns with different sizes and shapes and with a thickness of ca. 2.5 nm have been formed. The resulting lipid-modified molecular patterns are considered to be a first step towards obtaining stable biointerfacing patterns and studying biomolecular recognition.

Membranes, Artificial↗

PubMed2005

Electrochemical characterizations of nickel deposition on aromatic dithiol monolayers on gold electrodes.

The electronic properties of pristine and cross-linked (CL) self-assembled monolayers (SAMs) of [1,1';4',1' '-terphenyl]-4,4' '-dimethanethiol (TPDMT) on Au were studied by electrochemical measurements, including cyclic voltammetry and impedance spectroscopy. In addition, nickel deposition onto the TPDMT and CL-TPDMT substrates was investigated. In all cases, the TPDMT and CL-TPDMT films were found to be insulators, which effectively blocked the ionic permeation of electrolyte, preventing direct access of ions to the Au electrode. At the same time, CL-TPDMT is a better electric insulator than the pristine TPDMT SAM. The top Ni layer in the Ni/CL-TPDMT/Au arrangement was electrically isolated from the Au substrate, and no short circuits occurred. This layer was found to be conductive and relatively stable in the broad potential range in the electrolyte solution.

Journal Article↗

PubMed2005

Reversible protein adsorption and bioadhesion on monolayers terminated with mixtures of oligo(ethylene glycol) and methyl groups.

Surface-grafted, environmentally responsive polymers have shown great promise for controlling adsorption and desorption of macromolecules and cells on solid surfaces. In the paper, we demonstrate that certain mixed self-assembled monolayers (SAMs) of oligo(ethylene glycol) (OEG) and methyl-terminated alkanethiolates on gold form surfaces with switchable hydrophobicity and tendency for protein adsorption and cellular attachment. At temperatures above 32 degrees C, SAMs with a surface density of approximately 50% OEG adsorbed significant amounts of pyruvate kinase and lysozyme, whereas below this temperature, these same SAMs were resistant to the adsorption of these proteins. Furthermore, protein layers adsorbed to these SAMs above 32 degrees C were removed upon rinsing with water below this temperature. Similar results were seen for attachment and release of the marine bacterium, Cobetia marina. The change from nonresistance to adsorptive state of the SAMs was concomitant with a change in advancing water contact angle. Vibrational sum frequency generation spectroscopy suggests that the temperature-induced changes coincide with a disorder-to-partial order transition of the hydrated methylene chains of the OEG moieties within the SAMs. Mixed OEG-methyl SAMs represent both a convenient means of controlling macromolecular and cellular adsorption within the laboratory and a useful tool for relating adsorption properties to molecular structures within the SAMs.

Adhesives↗

PubMed2005

Effect of irradiation dose in making an insulator from a self-assembled monolayer.

A combination of functionalization and irradiation-induced cross-linking allows fabrication of stable metal film on top of an aromatic self-assembled monolayer, [1,1';4',1' '-terphenyl]-4,4' '-dimethanethiol (TPDMT) on Au. Using X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and ion-scattering spectroscopy the optimal irradiation dose for producing a stable metal overlayer was estimated to be 40-45 mC/cm2. This dose is necessary for complete 2D-polymerization and closure of transient channels, which would otherwise allow metal penetration into the SAM. What is also important, the majority of the thiol tail groups, responsible for 2D growth and chemical adherence of the metal film, remains intact even at this high dose. The optimal dose corresponds to a crossover in the response of the TPDMT film to ionizing radiation: the irradiation-induced processes progress fast at lower doses and saturate at higher doses.

Journal Article↗

PubMed2005

Innershell absorption spectroscopy of amino acids at all relevant absorption edges.

The C, N, and O K-edge near-edge X-ray absorption fine structure spectra of the 22 most common proteinogenic alpha-amino acids in the zwitterionic form collected from solvent-free polycrystalline powder films in the partial electron yield mode are reported. Spectral features common to all amino acids, as well as distinctive fingerprints of specific subgroups of these compounds, are presented and discussed.

Absorption↗

PubMed2005

Direct computer simulation of water-mediated force between supported phospholipid membranes.

The grand canonical Monte Carlo technique is used to calculate the water-mediated force operating between two supported 1,2-dilauroyl-DL-phosphatidylethanolamine (DLPE) membranes in the short separation range. The intra- and intermolecular interactions in the system are described with a combination of an AMBER-based force field for DLPE and a TIP4P model for water. The long range contributions to the electrostatic interaction energy are treated in the dipole-dipole group-based approximation. The total water-mediated force is analyzed in terms of its hydration component and the component due to the direct interaction between the membranes. The latter is, in addition, partitioned into the electrostatic, van der Waals, and steric repulsion contributions to give an idea of their relative significance in the water-mediated interaction of the membranes.

Computer Simulation↗

PubMed2005

Ultrafast core-hole-induced dynamics in water probed by x-ray emission spectroscopy.

The isotope effect and excitation-energy dependence have been measured in the oxygen K-edge x-ray emission spectrum (XES). The use of XES to monitor core decay processes provides information about molecular dynamics (MD) on an ultrafast time scale through the O1s lifetime of a few femtoseconds. Different nuclear masses give rise to differences in the dynamics and the observed isotope effect in XES is direct evidence of the importance of such processes. MD simulations show that even the excitation-energy dependence in the XES is mainly related to differences in core-excited-state dynamics.

Journal Article↗

PubMed2005

Surface chemistry of ultrathin films of histidine on gold as probed by high-resolution synchrotron photoemission.

Procedures for the vacuum deposition of thin histidine films on polycrystalline Au(111) and their characterization with high-resolution synchrotron-radiation-based photoelectron spectroscopy are reported. The chemical form of histidine (anionic vs zwitterionic) and the nature of its interactions with the substrate (strong ionic-covalent vs weak van der Waals bonding) in mono- and multilayer films are analyzed. It is shown that water adsorption on a pre-prepared histidine film at 100 K results in protonation of histidine molecules and partial formation of hydroxyl anions. These chemical effects are carefully differentiated from spectral changes associated with radiation damage of the histidine films.

Adsorption↗

PubMed2005

Characterization of trypsin immobilized on the functionable alkylthiolate self-assembled monolayers: a preliminary application for trypsin digestion chip on protein identification using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Self-assembled monolayers (SAMs) on coinage metal provide versatile modeling systems for studies of interfacial electron transfer, biological interactions, molecular recognition and other interfacial phenomena. Recently the bonding of enzyme to SAMs of alkanethiols onto Au electrode surfaces was exploited to produce a bio-sensing system. In this work, the attachment of trypsin to a SAMs surface of 11-mercaptoundecanoic acid was achieved using water soluble N-ethyl-N '-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide as coupling agent. The thickness of SAMs was determined by optical ellipsometer; contact angles of the modified Au surfaces were measured in air using a goniometer. The Second Harmony Generation data displays the last few percents of the alkylthiol molecules adsorbed and produced the complete monolayer by inducing the transition from a high number of gauche defects to an all-trans conformation. Using X-ray Photoelectron Spectroscopy (XPS) and Fourier-Transformed Infrared Reflection-Absorption and Attenuated Total Reflection Spectroscopes (FTIR-RAS and ATR), we examined the chemical structures of samples with different treatments. By matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), we demonstrated the digestion of bovine serum albumin (BSA) on the trypsin-immobilized SAMs surface. Experimental results have revealed that the XPS C1s core levels at 286.3 and 286.5 eV (Amine bond), 288.1 eV (Amide bond) and 289.3 eV (Carboxylic acid) illustrate the immobilization of trypsin. These data were also in good agreement with FTIR-ATR spectra for the peaks valued at 1659.4 cm(-1) (Amide I) and 1546.6 cm(-1) (Amide II). Using MALDI-TOF MS observations, analytical results have demonstrated the BSA digestion of the immobilized trypsin on the functionalized SAMs surface. For such surfaces, BSA was digested on the trypsin-immobilized SAMs surface, which shows the enzyme digestion ability of the immobilized trypsin. The terminal groups of the SAMs structure can be further functionalized with biomolecules or antibodies to develop surface-base diagnostics, biosensors, or biomaterials.

Biosensing Techniques↗

PubMed2005

A new polymer concept for coating of vascular stents using PTFEP (poly(bis(trifluoroethoxy)phosphazene) to reduce thrombogenicity and late in-stent stenosis.

OBJECTIVES: We sought to evaluate the new polymer PTFEP (poly(bis(trifluoroethoxy)phosphazene) for (1) its ability to reduce thrombogenicity and late in-stent stenosis and (2) its effect on endothelialization in a rabbit iliac artery model. MATERIALS AND METHODS: Nanocoated ( approximately 50 nm) and bare stainless-steel stents were implanted bilaterally in the iliac arteries of 30 New Zealand White rabbits (1, 4, 8, 12, and 16 weeks follow-up) and evaluated by angiography, light, and scanning electron microscopy. RESULTS: Bilateral stent placement was successful in 27 of 30 rabbits. Thrombus depositions occurred in none of the 27 coated but in 4 of the 27 bare stents (P=0.037). A normal angiogram was obtained in 18 of 22 coated stents at risk for restenosis (follow-up >or=4 weeks) but only in 13 of 22 bare stents (P=0.023). Marked restenosis (luminal loss >30%) was found in 6 bare stents (P=0.011) but not in any coated stents. The neointima was 47.7-73.9 mum on coated and 66.9-115.2 mum on bare stents (statistically significant at 4, 8, and 16 weeks). Scanning electron microscopy detected full endothelialization in all stents from 4 weeks on (22 stents in both groups). CONCLUSION: PTFEP nanocoating successfully showed thromboresistance and reduced late in-stent stenosis. Endothelialization was equal in both stent types. Studies in more human-like models and human feasibility studies in human arteries are encouraged.

Animals↗

PubMed2004

X-ray photoelectron spectroscopy and near-edge X-ray absorption fine structure study of water adsorption on pyridine-terminated thiolate self-assembled monolayers.

Adsorption of water on self-assembled monolayers (SAMs) of 4-(4-mercaptophenyl)pyridine on gold at low temperatures under ultrahigh vacuum conditions is studied by synchrotron radiation X-ray photoelectron and absorption spectroscopy. Water adsorption induces a strong modification of the chemical state of the pyridine N atoms at the SAM/ice interface, indicative for strong H bonding and partial proton transfer between water molecules and pyridine moieties. Additionally, the initial molecular orientation within the SAM is changed upon formation of an adsorbed water multilayer.

Absorption↗

PubMed2004

Modification of aliphatic self-assembled monolayers by free-radical-dominant plasma: the role of the plasma composition.

Modification of octadecanethiolate self-assembled monolayers on Au by nitrogen-oxygen or argon-oxygen downstream microwave plasma with a low oxygen content (estimated below several percent) has been studied by synchrotron-based high-resolution X-ray photoelectron spectroscopy and water contact angle measurements. For both types of plasma, the primary processes were found to be the loss of conformational and orientational order and the oxidation of the alkyl matrix and headgroup-substrate interface. At the same time, the film modification occurred much faster and with different intermediates for the nitrogen plasma than for the argon plasma. The reasons for these differences are considered in terms of the different reactivities and different efficiencies of the energy transfer between the plasma constituents in these two types of plasma.

Journal Article↗

PubMed2004

Protein deformation of lipid hybrid bilayer membranes studied by sum frequency generation vibrational spectroscopy.

Structural deformations of lipid hybrid bilayer membranes induced by signal peptideless (SPL) proteins have been studied for the first time using the inherently surface specific nonlinear optical technique of sum frequency generation vibrational spectroscopy. Specifically, deformations of 1,2-distearoylphosphatidylglycerol(DSPG) membranes induced by interaction with FGF-1, a SPL protein which is released asa function of cellular stress through a nonclassical pathway, have been investigated. FGF-1 was found to induce lipid alkyl chain deformations in previously highly ordered DSPG membranes at the extremely low concentration of 1 nM at 60 degrees C. The deformation process was shown to exhibit a degree of reversibility upon removal of the protein by rinsing with buffer solution.

Fibroblast Growth Factor 1↗