Probing the lipid chemistry of neurotoxin-induced hippocampal lesions using multimodal imaging mass spectrometry.

The environmental toxin β-N-methylamino-L-alanine (BMAA) has been causatively linked to neurodegenerative disease pathology. In a rat model, neonatal BMAA exposure resulted in selective uptake in the hippocampal formation and caused learning and memory impairments in adult animals. Moreover, high dose neonatal BMAA exposure resulted in formation of protein inclusions in the CA1 region of the adult hippocampus.

Time-of-flight secondary ion mass spectrometry based molecular histology of human spinal cord tissue and motor neurons.

Secondary ion mass spectrometry is a powerful method for imaging biological samples with high spatial resolution. Whole section time-of-flight-secondary ion mass spectrometry (TOF-SIMS) scans and multivariate data analysis have been performed on the human spinal cord in order to delineate anatomical regions of interest based on their chemical distribution pattern. TOF-SIMS analysis of thoracic spinal cord sections was performed at 5 μm resolution within 2 h.

Imaging mass spectrometry in neuroscience.

Imaging mass spectrometry is an emerging technique of great potential for investigating the chemical architecture in biological matrices. Although the potential for studying neurobiological systems is evident, the relevance of the technique for application in neuroscience is still in its infancy. In the present Review, a principal overview of the different approaches, including matrix assisted laser desorption ionization and secondary ion mass spectrometry, is provided with particular focus on their strengths and limitations for studying different neurochemical species in situ and in vitro.

Surface relaxation influenced by surface states.

A detailed theoretical investigation of the relaxation of the simple metal surface Al(100) is presented. We show the influence of electronic surface states in this context. The sign and magnitude of the relaxation of the topmost atomic layers is mainly determined by the rearrangements of the surface state charge.

Energy distributions in multiple photon absorption experiments.

Photofragmentation experiments on molecules and clusters often involve multiple photon absorption. The distributions of the absorbed number of photons are frequently approximated by Poisson distributions. For realistic laser beam profiles, this approximation fails seriously due to the spatial variation of the mean number of absorbed photons across the laser beam.

Computational studies of carbon nanotube-hydrocarbon bond strengths at nanotube ends: effect of link heteroatom and hydrocarbon structure.

Semiempirical and density functional electronic structure theory methods were used to study SWNT-X--R bond strengths, where the single-walled carbon nanotube (SWNT) had an armchair or zigzag structure, the link heteroatom X was O, N(H), or S and the hydrocarbon chain R was CH(2)CH(3), CH(OH)CH(3), CHCH(2), or CH(CF(3))CH(3). In all systems the hydrocarbon was bonded to the end of the nanotube. The SWNT-X--R bond (that is, the bond joining the link atom to the hydrocarbon) is more than 0.

Electrochemical potentials and pressures of biofluids from common experimental data.

Many biosystems are complex mixtures of disparate biofluids. To study contact and transport phenomena in these mixtures, one has to apply much information on the biofluids which are components of the mixtures. A lot of the corresponding data can be extracted by means of experiments.

Mode-coupling theory and polynomial fitting functions: a complex-plane representation of dielectric data on polymers.

Recently, it has been shown that the higher-order A3 and A4 scenarios of the mode-coupling theory (MCT) are in many cases capable of providing a good description of the complicated dielectric spectra often encountered in polymeric systems. In this paper, more data from dielectric measurements on poly(ethylene terephthalate), poly(vinylidene fluoride), Nylon-66, poly(chlorotrifluoroethylene) (PCTFE), and the polymer gel system poly(acrylonitrile)-ethylene carbonate-propylene carbonate are evaluated within the A4 scenario of the MCT. For all these systems, very good agreement is found between the theoretical and experimental spectra.

A sightseeing tour in the world of clusters--serendipity and scientific progress.

The discovery of the fullerenes in 1985 by Kroto et al. and the development of a method for producing macroscopic amounts in 1990 by Krätschmer et al. opened a new area of carbon research and the possibility of producing new materials with unique properties.

Crystal structure of the disulfide bond-deficient azurin mutant C3A/C26A: how important is the S-S bond for folding and stability?

Azurin has a beta-barrel fold comprising eight beta-strands and one alpha helix. A disulfide bond between residues 3 and 26 connects the N-termini of beta strands beta1 and beta3. Three mutant proteins lacking the disulfide bond were constructed, C3A/C26A, C3A/C26I and a putative salt bridge (SB) in the C3A/S25R/C26A/K27R mutant.

The membrane topology of proton-pumping Escherichia coli transhydrogenase determined by cysteine labeling.

The membrane topology of proton-pumping nicotinamide-nucleotide transhydrogenase from Escherichia coli was determined by site-specific chemical labeling. A His-tagged cysteine-free transhydrogenase was used to introduce unique cysteines in positions corresponding to potential membrane loops. The cysteines were reacted with fluorescent reagents, fluorescein 5-maleimide or 2-[(4'-maleimidyl)anilino]naphthalene-6-sulfonic acid, in both intact cells and inside-out vesicles.

Mapping of residues in the NADP(H)-binding site of proton-translocating nicotinamide nucleotide transhydrogenase from Escherichia coli. A study of structure and function.

Conformational changes in proton pumping transhydrogenases have been suggested to be dependent on binding of NADP(H) and the redox state of this substrate. Based on a detailed amino acid sequence analysis, it is argued that a classical betaalphabetaalphabeta dinucleotide binding fold is responsible for binding NADP(H). A model defining betaA, alphaB, betaB, betaD, and betaE of this domain is presented.

Interactions of reduced and oxidized nicotinamide mononucleotide with wild-type and alphaD195E mutant proton-pumping nicotinamide nucleotide transhydrogenases from Escherichia coli.

The interaction of reduced nicotinamide mononucleotide (NMNH), constituting one half of NADH, with the wild-type and alphaD195E proton-pumping nicotinamide nucleotide transhydrogenase from Escherichia coli was investigated. Reduction of thio-NADP+ by NMNH was catalysed at approximately 30% of the rate with NADH. Other activities including proton pumping and the cyclic reduction of 3'-acetyl-pyridine-NAD+ by NMNH in the presence of NADP+ were more strongly inhibited.

Structural changes in hemoglobin during adsorption to solid surfaces: effects of pH, ionic strength, and ligand binding.

We have studied the adsorption of two structurally similar forms of hemoglobin (met-Hb and HbCO) to a hydrophobic self-assembled methyl-terminated thiol monolayer on a gold surface, by using a Quartz Crystal Microbalance (QCM) technique. This technique allows time-resolved simultaneous measurements of changes in frequency (f) (c.f.

Charge displacements in interfacial layers containing reaction centers.

Reaction centers from the photosynthetic bacterium Rhodobacter sphaeroides were oriented in phospholipid interfacial layers adsorbed to a Teflon film separating two electrolyte-filled compartments of a Teflon cell. Light-induced voltage changes were measured as a function of time across electrodes immersed in the cell compartments. The experimental system is characterized both experimentally and theoretically to relate the measured signals to the light-induced displacement currents in the reaction centers.

Electron transfer in ruthenium-modified spinach plastocyanin mutants.

Four site-directed mutants of spinach plastocyanin, Pc(Leu12His), Pc(Leu15His), Pc(Thr79His), and Pc(Lys81His), have been modified by covalent attachment of a photoactive [Ru(bpy)2(im)]2+ complex at the surface-exposed histidine residues. The Pc-Ru complexes were characterized with optical absorption, CD, and EPR spectroscopy and their spectra were found to be similar to the unmodified proteins except in the case of the Pc(Leu12His) mutant which lost the Cu ion irreversibly during the Ru modification. Electron transfer (ET) within the other Pc-Ru complexes was studied with time-resolved optical spectroscopy, using an external-quencher approach.

Role of the pathway through K(I-362) in proton transfer in cytochrome c oxidase from R. sphaeroides.

In this study we have combined the use of site-directed mutants with time-resolved optical absorption spectroscopy to investigate the role of the protonatable subunit-I residues lysine-362 (K(I-362)) and threonine-359 (T(I-359)) in cytochrome c oxidase from Rhodobacter sphaeroides in electron and proton transfer. These residues have been proposed to be part of a proton-transfer pathway in cytochrome oxidases from Paracoccus denitrificans and bovine heart. Mutation of K(I-362) and T(I-359) to methionine and alanine, respectively, results in reduction of the overall turnover activities to <2% and approximately 35%, respectively, of those in the wild-type enzyme.

The effect of the metal ion on the folding energetics of azurin: a comparison of the native, zinc and apoprotein.

The unfolding by guanidine hydrochloride (GuHCl) and the refolding on dilution of zinc and apoazurin have been monitored by far-UV circular dichroism (CD). With the native protein, the unfolding was followed by CD and optical absorption in the visible spectral region. With the zinc protein, the reversible unfolding has also been followed by tryptophan fluorescence and NMR.

Structural and catalytic properties of the expressed and purified NAD(H)- and NADP(H)-binding domains of proton-pumping transhydrogenase from Escherichia coli.

Proton-pumping nicotinamide nucleotide transhydrogenase from Escherichia coli contains three domains: the hydrophilic domains I and III harbor the binding sites for NAD(H) and NADP(H), respectively, and domain II represents the membrane-spanning region. Proton translocation involves primarily domain II but possibly also domain III, which contains the essential betaAsp392 residue. In the present investigation, the major portions of domain I (EcTHSalpha1 and EcTHSalpha2) and domain III (EcTHSbeta1) were overexpressed in E.

Electron transfer between spinach plastocyanin mutants and photosystem 1.

Two distinct regions of plastocyanin, one hydrophobic and one acidic, are generally thought to be involved in the electron-transfer reactions with its physiological partners, cytochrome f and photosystem 1. To probe the importance of the hydrophobic patch in the reaction with photosystem 1, seven mutant plastocyanin proteins have been constructed with the following mutations: Gly7Ala, Gly8Asp, Ser11Asp, Ser11Gly, Pro36Gly, Ser85Thr and Gln88Asn. The electron-transfer reaction was investigated by transient flash-photolysis absorption spectroscopy.