Professor Adya is the Leader of the Condensed Matter Group and BIONTHE (Bio- and Nano-Technologies for Health & Environment) Centre at the University of Abertay Dundee (UAD). He is a Professor of Nanotechnology in the Division of Biotechnology & Forensic Sciences of the School of Contemporary Sciences at the UAD. He is internationally recognised for his nanoscopic structural work on a wide variety of systems ranging from biological systems and processes (proteins, yeast cells, Candida cells - pathogenic and non-pathogenic, virus-encoded proteins, protein-RNA interactions, etc.), molten salts, non-aqueous electrolyte solvents and solutions (NAES) to molecular liquids and liquid mixtures, by using Atomic Force Microscopy (AFM), optical & fluorescence microscopy, neutron diffraction (ND), neutron reflection (NR), small angle neutron scattering (SANS), X-ray diffraction (XRD), XAFS measurements, and Molecular Dynamics (MD) Simulations. He has a formidable array of national and international collaborators working in these fields. He derives his enthusiasm through these links and collaborations, and enjoys passing this drive and motivation to the students through his teaching. He has given innumerable invited, plenary, opening, and key-note lectures at international conferences/symposia, universities, and research institutions around the globe. He is a member of the EPSRC peer-review panel and referees research articles for various international journals. He has taught a wide range of subjects in Chemistry, and Forensic Sciences, such as Classical Thermodynamics, Statistical Thermodynamics, Ionic Equilibria, Applied Electrochemistry, Electroanalytical Techniques, Chemical Kinetics, Industrial Chemistry, Environmental Chemistry, Molecular Spectroscopy, Computer Chemical Modelling, Applied Surface Chemistry, Industrial Chemicals, Analytical Chemistry, Forensic Applications of Image Processing and Enhancement, Firearms, Ballistics, and Gunshot Residues, History of Microscopy, Microscopic Techniques, Chemical Enhancement of Images followed by Laser Detection, Neutron Scattering: Techniques and Applications. In addition, he also published five Chemistry text books at the Secondary and Senior Secondary School level, and has more than 100 research publications to his credit.
Abstract: Atomic force microscopic investigation of commercial pressure sensitive adhesives for forensic analysis
Elisabetta Canetta, Ashok K. Adya*
Division of Biotechnology & Forensic Sciences, School of Contemporary Sciences, University of Abertay Dundee, Bell Street, Dundee DD1 1HG, U. K.
*Corresponding author. Tel.: +44 0 1382 308653; fax: +44 0 1382 308663.
Received 26 July 2010; received in revised form 12 January 2011; accepted 25 January 2011. published online 22 February 2011.
Abstract
Pressure sensitive adhesive (PSA), such as those used in packaging and adhesive tapes, are very often encountered in forensic investigations. In criminal activities, packaging tapes may be used for sealing packets containing drugs, explosive devices, or questioned documents, while adhesive and electrical tapes are used occasionally in kidnapping cases. In this work, the potential of using atomic force microscopy (AFM) in both imaging and force mapping (FM) modes to derive additional analytical information from PSAs is demonstrated. AFM has been used to illustrate differences in the ultrastructural and nanomechanical properties of three visually distinguishable commercial PSAs to first test the feasibility of using this technique. Subsequently, AFM was used to detect nanoscopic differences between three visually indistinguishable PSAs.
Article Outline
1. Introduction
2. Experimental
2.1. Commercial pressure sensitive adhesives
2.2. Atomic force microscopy (AFM) imaging
2.3. AFM force mapping (AFM-FM)
2.4. Nanomechanical properties
3. Results and discussion
3.1. Nanostructure of three visually distinguishable PSAs
3.2. Nanostructure of three visually indistinguishable OPP transparent PSAs
3.3. Nanomechanical properties of three visually distinguishable PSAs
3.4. Nanomechanical properties of three visually indistinguishable OPP transparent PSAs
4. Conclusions
Acknowledgements
References
Keywords: Atomic force microscopy (AFM), Force mapping, Nanotechnology, Pressure sensitive adhesive (PSA), Mechanical properties, Items of recovery
Abstract: 1H, 2H and 13C NMR spectra have been used to test the Ni2+ solvation shell composition in the 1.1 molal methanol solution of NiCl2. It has been confirmed that Cl- anion takes part in the nearest environment of Ni2+ cation at all the temperatures investigated. Using 2H NMR allowed us to detect for the first time OD-signal of methanol in the primary solvation shell of Ni2+ cation. Both 2H and 13C NMR spectra show that the composition of the cation solvation shell becomes more complicated at temperatures lower than 220 K.
Abstract: Abstract:
The expansive growth and differentiation potential of human embryonic stem cells (hESCs) make them a promising source of cells for regenerative medicine. However, this promise is off set by the propensity for spontaneous or uncontrolled differentiation to result in heterogeneous cell populations. Cell elasticity has recently been shown to characterize particular cell phenotypes, with undifferentiated and differentiated cells sometimes showing significant differences in their elasticities. In this study, we determined the Young's modulus of hESCs by atomic force microscopy using a pyramidal tip. Using this method we are able to take point measurements of elasticity at multiple locations on a single cell, allowing local variations due to cell structure to be identified. We found considerable differences in the elasticity of the analyzed hESCs, reflected by a broad range of Young's modulus (0.05-10âkPa). This surprisingly high variation suggests that elasticity could serve as the basis of a simple and efficient large scale purification/separation technique to discriminate subpopulations of hESCs.
Abstract: X-ray absorption fine structure studies of molten metal fluorides containing the materials related to nuclear engineering are intensively summarized. By using XAFS spectra data of divalent and trivalent cation metal fluorides in molten state which have been collected by authorsâ group for a few years, local structure have been extracted and discussed systematically in conjunction with other spectroscopic
studies and numerical calculations. In molten divalent fluorides, tetrahedral coordination of fluorides around a cation is predominant. In the case of pure molten trivalent fluorides, structure withmore than 6-coordination has been suggested in some cases, but octahedral coordination structure is much stabilized at heavier rare earth metal fluorides. By mixing with alkali metal fluorides, it is a general trend that interionic distances keep constant, but coordination number of fluorides decreases. In experimental chapter, all the details of sample preparation, furnace installation, X-ray optics setups and data analyses procedures are explained. Finally, future expectations of XAFS technique are also suggested.
Abstract: Nanoscopic changes in the cell surface morphology of the yeasts, Saccharomyces cerevisiae (strain NCYC 1681), and Schizosaccharomyces pombe (strain DVPB 1354), due to their exposure to varying concentrations of hydrogen peroxide (oxidative stress) were investigated using an Atomic Force Microscope (AFM). Increasing hydrogen peroxide concentration led to a decrease in cell viabilities and mean cell volumes, and an increase in the surface roughness of the yeasts. In addition, AFM studies revealed that oxidative stress caused cell compression in both S. cerevisiae and Schiz. pombe cells and an increase in the number of aged yeasts. These results confirmed the importance, and usefulness of AFM in investigating the morphology of stressed microbial cells at the nanoscale. The results also provided novel information on the relative oxidative stress tolerance of S. cerevisiae and Schiz. pombe.
Abstract: The ability of the atomic force microscope (AFM) to investigate the nanoscopic morphological changes in the surfaces of fabrics was examined for the first time. This study focussed on two natural (cotton and wool), and a regenerated cellulose (viscose) textile fibres exposed to various environmental stresses for different lengths of times. Analyses of the AFM images allowed us to measure quantitatively the surface texture parameters of the environmentally stressed fabrics as a function of the exposure time. It was also possible to visualise at the nanoscale the finest details of the surfaces of three weathered fabrics and clearly distinguish between the detrimental effects of the imposed environmental conditions. This study confirmed that the AFM could become a very powerful tool in forensic examination of textile fibres to provide significant fibre evidence due to its capability of distinguishing between different environmental exposures or forced damages to fibres.
Abstract: Fibrillarin, one of the major proteins of the nucleolus, has methyltransferase activity directing 2'-O-ribose methylation of rRNA and snRNAs and is required for rRNA processing. The ability of the plant umbravirus, groundnut rosette virus, to move long distances through the phloem, the specialized plant vascular system, has been shown to strictly depend on the interaction of one of its proteins, the ORF3 protein (protein encoded by open reading frame 3), with fibrillarin. This interaction is essential for several stages in the groundnut rosette virus life cycle such as nucleolar import of the ORF3 protein via Cajal bodies, relocalization of some fibrillarin from the nucleolus to cytoplasm, and assembly of cytoplasmic umbraviral ribonucleoprotein particles that are themselves required for the long-distance spread of the virus and systemic infection. Here, using atomic force microscopy, we determine the architecture of these complexes as single-layered ringlike structures with a diameter of 18-22 nm and a height of 2.0+/-0.4 nm, which consist of several (n=6-8) distinct protein granules. We also estimate the molar ratio of fibrillarin to ORF3 protein in the complexes as approximately 1:1. Based on these data, we propose a model of the structural organization of fibrillarin-ORF3 protein complexes and discuss potential mechanistic and functional implications that may also apply to other viruses.
Abstract: The high-resolution quasi-elastic neutron scattering (QENS) technique has been applied to study the translational diffusion of methanol protons in pure methanol (MeOH) at 223 and 297 K, and in 0.3 and 1.3 molal non-aqueous electrolyte solutions (NAESs) of NiCl2 in methanol at 297 K. Molecular dynamics (MD) simulations, in conjunction with the present QENS results and our previously published structural results obtained by neutron diffraction isotopic substitution (NDIS) experiments, have been carried out in the NVT ensemble to explore the particle dynamics and microscopic structures of the experimentally investigated systems. The simulated structure of the ~1.35 molal NiCl2âMeOH NAES has been compared with the structures of Ni2+ and Clâ coordination shells in ~1.4 molal NAES obtained earlier by the NDIS technique.
Abstract: The detrimental effects of ethanol toxicity on the cell surface morphology of Saccharomyces cerevisiae (strain NCYC 1681) and Schizosaccharomyces pombe (strain DVPB 1354) were investigated using an atomic force microscope (AFM). In combination with culture viability and mean cell volume measurements AFM studies allowed us to relate the cell surface morphological changes, observed on nanometer lateral resolution, with the cellular stress physiology. Exposing yeasts to increasing stressful concentrations of ethanol led to decreased cell viabilities and mean cell volumes. Together with the roughness and bearing volume analyses of the AFM images, the results provided novel insight into the relative ethanol tolerance of S. cerevisiae and Sc. pombe.
Abstract: Atomic Force Microscopy (AFM) has emerged as a powerful biophysical tool in biotechnology and medicine to investigate the morphological, physical, and mechanical properties of yeasts and other biological systems. However, properties such as, yeasts' response to environmental stresses, metabolic activities of pathogenic yeasts, cell-cell/cell-substrate adhesion, and cell-flocculation have rarely been investigated so far by using biophysical tools. Our recent results obtained by AFM on one strain each of Saccharomyces cerevisiae and Schizosaccharomyces pombe show a clear correlation between the physiology of environmentally stressed yeasts and the changes in their surface morphology. The future directions of the AFM related techniques in relation to yeasts are also discussed.
Abstract: Morphological changes in the cell surfaces of the budding yeast Saccharomyces cerevisiae (strain NCYC 1681), and the fission yeast Schizosaccharomyces pombe (strain DVPB 1354), in response to thermal and osmotic stresses, were investigated using an atomic force microscope. With this microscope imaging, together with measurements of culture viability and cell size, it was possible to relate topological changes of the cell surface at nanoscale with cellular stress physiology. As expected, when the yeasts were exposed to thermostress or osmostress, their viability together with the mean cell volume decreased in conjunction with the increase in thermal or osmotic shock. Nevertheless, the viability of cells stressed for up to 1 h remained relatively high. For example, viabilities were >50% and >90% for the thermostressed, and >60% and >70% for the osmostressed S. cerevisiae and Schiz. pombe, respectively. Mean cell volume measurements, and bearing and roughness analyses of atomic force microscope images of stressed yeasts indicate that Schiz. pombe may be more resistant to physical stresses than S. cerevisiae. Overall, this study has highlighted the usefulness of atomic force microscope in studies of yeast stress physiology.
Abstract: Transmission XAFS measurements were performed on lanthanum chloride (LaCl3) and LaCl3-Li2O mixture at various temperatures using La-K x-ray absorption edge. A distinct phase shift in the EXAFS oscillations was observed in going from the solid phase to the molten phase in LaCl3. The results of curve fitting to the predominant peak in the structure function of LaCl3 in real space, corresponding to the La3+-Clâ 1st coordination shell, reveal that both the inter-ionic distance and coordination number of chloride ions around a lanthanum ion decreased with increase in temperature to above its melting point. The short-range structure of LaCl3-Li2O (xLi2O = 5 mol%) mixture appears to be almost similar to that observed in pure LaCl3.
Abstract: Molecular dynamics (MD) simulations of dimethyl sulfoxide (DMSO) solutions of Li+, Me4N+, BPh4â, big spherical ions of the same size but different charge, such as S+, Sâ, S0 have been performed at 298 K in NVT ensembles by using a four-interacting-sites model of DMSO and reaction field method for Coulombic interactions. Similar simulations were also performed on neat DMSO in which one DMSO molecule acted as a solute. The microscopic structures of ion-solvation shells have been analysed by employing a concept of co-ordination centres and characteristic vectors of the solvent molecule. Results are given for the atomâatom and ionâatom radial distribution functions (RDFs), orientation of the DMSO molecules and their geometrical arrangements in the first solvation shells of the ions. For the solvophilic Li+, a highly symmetric and well-pronounced first solvation shell (FSS) with fixed co-ordination number is observed. The co-ordination number and geometry of the FSS of lithium ion is strongly defined by the short-range non-Coulombic interactions between the ion and the surrounding DMSO molecules. The results show the importance of charge distribution in the solvent molecule and consequently the sign of ionic charge in creating local order around the solvated ion. It is found that the DMSO solvates S+ better than Sâ, which is better solvated than S0. The solvophobic nature of the big multiatomic ions in non-aqueous media creates the possibility of the solvent molecules penetrating into the solute that is typically observed from our simulations not only for the charged species like Me4N+ and BPh4â, but also for the neutral solute represented by the DMSO molecule in neat DMSO.
Abstract: Molecular dynamics (MD) simulations of pure dimethyl sulphoxide (DMSO) and solutions of Na+, Ca2+, Cl-, NaCl and CaCl2 in DMSO have been performed at 298.15 K and 398.15 K in NVT ensembles by using a four-interaction-site model of DMSO and reaction field method for Coulombic interactions. The structure of solvent, ion-solvation shells and ion-pairs have been analysed by employing a concept of coordination centres and characteristic vectors of the solvent molecule. Results are given for atom-atom (corresponding to DMSO), ion-atom and ion-ion radial distribution functions (RDFs), orientation of the DMSO molecules and their geometrical arrangements in the first solvation shells of the ions (Na+, Ca2+, Cl-). A preferential formation of cyclic dimers with antiparallel alignment between dipole moments of nearest-neighbour molecules in the pure solvent is found. Geometrical models of the first coordination shells of the ions in 'infinitely dilute solutions' are proposed. Ion-ion RDFs in NaCl-DMSO and CaCl\2-DMSO solutions reveal the presence of both solvent separated (SSIP) and contact (CIP) ion pairs. The structures of the solvation shells of such ion pairs are also discussed.
Abstract: XAFS spectroscopy has increasingly been utilised to elucidate the nearest-neighbour structure in the condensed phases. In this paper, the XAFS spectra of NdCl3 and DyCl3 in both the solid and the liquid phases measured at the Nd and Dy L(III) absorption edges on beam line BM29 of the European Synchrotron Radiation Facility (ESRF) are presented. The Fourier transformed radial structure functions, phi(r) show that the prominent peaks corresponding to M-Cl (M: Nd or Dy) first shell contribution are shifted to shorter distances in the liquid melts as compared to those found in the corresponding solids. Similar behaviour has also been observed from other diffraction techniques in typical ionic melts such as NaCl. From the temperature dependence of the radial structure functions it is clear that the change in the M-Cl distance on melting is much larger in NdCl3 than that in DyCl3.
Abstract: The X-ray absorption fine structure(XAFS) spectra of neodymium and dysprosium chlorides(NdCl3 and DyCl3) in both the solid and the liquid phases, measured over a range of temperatures at the Nd and Dy LIII absorption edges on beam line BM29 of the European Synchrotron Radiation Facility(ESRF) are presented. The Fourier transformed radial structure functions .PHI.(r) show that the prominent peaks corresponding to the M-Cl(M: Nd or Dy) first-shell contribution are shifted to shorter distances in the liquid melts as compared to those in the solids. From the temperature dependence of the radial structure functions it is clear that the change in the M-Cl distance on melting is much larger in NdCl3 than in DyCl3.
Abstract: The structure of molten lithium nitrate at 573 K has been investigated by applying the technique of neutron diffraction to five isotopically enriched samples: NLiNNO3, 0LiNNO3, 7LiNNO3, 7Li15NO3 and 0Li15NO3. The ion-ion and ion-counterion partial structure factors relating to gLi-Li(r), gLi-N(r), gLi-O(r) partial pair correlation functions have been successfully extracted from the experimental data by the isotopic difference methods. Some general conclusions are made about the detailed structure of molten lithium nitrate. Comparison is also made with earlier X-ray and neutron diffraction and molecular dynamics (MD) simulation studies. In particular, the nearest-neighbour Li-O and Li-Li distances of 1·86 à and 3·86 à reported in MD study are significantly less than the values of 2·1 à and 4·1 Ã, respectively found in the present study. This we feel is a result of the uncertainty in the effective pair potentials used in the MD simulation. The nearest-neighbour distances rLi-O = 2·1 ± 0·1 à and rLi-N = 2·8 ± 0·1 à obtained in the present study on a stable nuclear reactor source compare well with those obtained by Kameda et al. [1] from a recent time-of-flight neutron diffraction study on a spallation source. The lithium monovalent cation is surrounded on an average by four nitrate (NO3-) ions; one oxygen atom in each of these NO3- ions facing towards Li+. Although, these results are found to be consistent with those of Kameda et al., certain discrepancies between the two results become apparent in the next-nearest neighbour shells. Additionally, the closest Li+-Li+ approach rLi-Li = 4·1 ± 0·2 à is smaller than that for NO3- - NO3-, rN-N = 4·8 ± 0·2 à [1]. The space and time averaged local structure of LiNO3 in the molten state is found to be appreciably different from that in its crystalline state.
Abstract: A neutron diffraction study of a 50 mol kgâ1 aqueous solution of deuterated ammonium nitrate [ca. 1 : 1 molecular ratio of D2O : N(1)D4N(2)O3 which is the saturation solubility at ca. 70 °C] was carried out at 100 °C. The first- and second-order isotopic difference methods of neutron diffraction were applied to the nitrogen nuclei of both the ammonium and nitrate ions. The results derived from the total and first-order difference diffraction functions show the existence of stable ND+4 and NOâ3 ions in the solution. Structural information concerning the ammonium ionâwater and nitrate ionâwater coordination was obtained from the first-order differences, and the results indicate a relatively weak hydration shell for these ions.A calculation of the second order difference function enabled the determination of the cross pair radial distribution function gN(1)N(2)(r) from which it was concluded that the nearest-neighbour N(1)âN(2) distance increases significantly on the addition of D2O to ND4NO3.
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Abstract: A neutron diffraction study of the atomic structure of deuterated molten ammonium nitrate (N(1)D4N(2)O3) was carried out at 453 K. The first and second order isotopic difference methods of neutron diffraction were applied to the nitrogen nuclei of the ammonium and nitrate ions. The results of the total and the first order differences demonstrate the existence of stable ND+4 and NO-3 ions in the melt. The ND+4 ions conform to a tetrahedral geometry and the NO-3 ions retain a D3h symmetry arising from a triangular geometry. The second order difference enabled the determination of the 'cross' pair distribution function gN(1)N(2)(r), from which it was concluded that the crystal structure relaxes significantly on melting.
Abstract: Abstract:
Nanotechnology tools, such as Atomic Force Microscopy (AFM), are now becoming widely used in life sciences and biomedicine. AFM is a versatile technique that allows studying at the nanoscale the morphological, dynamic, and mechanical properties of biological samples, such as living cells, biomolecules, and tissues under physiological conditions. In this article, an overview of the principles of AFM will be first presented and this will be followed by discussion of some of our own recent work on the applications of AFM imaging to biomedicine.
Abstract: Estimation of the time of death of the victim of a murder or the age of bloodstains left at a crime scene is one of the most significant problems encountered in forensic medicine, science, and law over a century. Although various techniques have been used to help determine reliably the age of dried bloodstains, none has ever been recognised to be authentic enough for use in routine forensic case work. Nanotechnology could possibly provide a solution to solve this problem.
We have investigated the effectiveness and possible application of Atomic Force Microscopy (AFM) in the age determination of dried blood in forensic casework. AFM is a newly emerged and rapidly expanding nanotechnique with the unique ability to visualise the ultrastructure of a sample at the nano-scale and to measure its nanomechanical properties, such as erythrocyte cell-wall elasticity, which can be potentially useful for forensic application.
In order to mimic ârealâ crime scenes, drops of whole blood obtained from a healthy donor were reverse-smeared on glass, mica, and stainless steel substrates and then exposed to uncontrolled outdoor environmental conditions for different lengths of times ranging from 0 weeks (control) up to 7 weeks. Changes observed in the ultrastructure and nanomechanics of the red blood cells (RBCs) were quantified and related to the time domain. The cells lost their doughnut-shapes, became flatter, and the central grooves shrank with time. The elasticity of the cells decreased over time, showing that with ageing the cell membrane grew stiffer. These changes were found to be time and surface dependent.
Abstract: The New Non-Polarizable Force Field Model of Imidazolium-Based Ionic Liquids
V. V. Chaban, I. V. Voroshylova, A. K. Adya, O. N. Kalugin
Room temperature ionic liquids (ILs) have attracted much attention over the past few years. The most promising areas of their application, amongst many, are lithium batteries, supercapacitors, lubricants, actuators, sensors, reaction media, and hypergolic propellants. Their excellent thermal and electrochemical stability, negligible vapor pressure, dissolution in many solvents, and low flammability are the most exciting properties of these modern alternative materials. Molecular dynamics (MD) simulations have become a common practice to reliably probe the effects of various cation/anion tandems on the structure and dynamic properties of the ILs.
Many polarizable [1] and non-polarizable [2,3] force fields (FFs) have already been developed in order to perform extensive simulations of ILs by means of the classical MD and Monte Carlo techniques. While their structure and thermodynamics properties are well reproduced in almost every simulation, the main problem of all the non-polarizable FFs remains in the substantial (up to one order of magnitude) underestimation of the self-diffusion coefficients and specific electrical conductivity, and a considerable overestimation of the shear viscosity. These deviations are usually explained by the total neglect of electronic polarization effects in the classical MD simulations. The new polarizable FFs allow us to overcome this problem, although the usage of such techniques is much more time-consuming. Besides, for some classes of ILs, some inexplicable divergence with experimental data (up to 50%) is still observed [1].
The primary goal of our work is to develop a procedure to account for ILs polarization effects in the framework of the classical MD. Through this work, we illustrate its successful operation on two imidazolium-based ILs, 1-methyl-3-ethylimidazolium tetrafluoroborate [EMIM][BF4] and 1-methyl-3-buthylimidazolium tetrafluoroborate [BMIM][BF4]. The initial electrostatic charges on all the cation and anion interaction sites were reduced according to the charge distributions derived from the Car-Parrinello MD simulations of the bulk ILs. The charges were obtained from electrostatic potential fit by using 10 uniformly spaced system configurations and then averaged. The obtained charge distributions together with Lennard-Jones (12, 6) parameters from AMBER force field excellently reproduced the experimental properties of both the [EMIM][BF4] and [BMIM][BF4] systems for self-diffusion, electrical conductivity, and shear viscosity over a wide temperature range (from 298 K up to 400 K). Being successful with the imidazolium-based ILs, we believe that the proposed procedure should become useful for other classes of ILs and similar compounds where the polarizability effects play a key role.
1. Borodin, O. J. Phys. Chem. B 2009, 113, 11463â11478
2. Liu, Zh.; Huang, Sh.; Wang, W. J. Phys. Chem. B 2004, 108, 12978â12989
Abstract: The high-resolution quasi-elastic neutron scattering (QENS) technique has
been applied to study the translational and rotational diffusion of methanol
molecules in pure methanol (MeOH) at different temperatures and various
NiCl2 concentrations. Molecular dynamics (MD) simulations have been carried
out in the NVT ensemble to explore the particle dynamics and microscopic
structures of the experimentally investigated systems.
The translational diffusion coefficients derived from the QENS measure-
ments of pure MeOH at the different temperatures agree well with the values
reported in literature. Our results clearly indicate that the translational dif-
fusion coefficient of methanol decreases (i) with decrease in temperature, and
(ii) with increase in the concentration of NiCl2 in MeOH, whereas the rota-
tional diffusion coefficient is not so affected by variation of temperature or
electrolyte concentration. The present MD simulations confirm the above ex-
perimental findings.
The MD results show that mainly the solvent molecules present in the bulk
govern the dynamic behaviour of MeOH molecules in its electrolyte solutions.
The translational diffusion coefficients of the Ni2+, of MeOH molecules in the
first solvation shell of Ni2+, and also of its counter-ion, the Clâ, are very close
to each other and follow similar trends with change in concentration of the
electrolyte.
Analysis of molecule dynamics in terms of diffusion coefficients and auto-
correlation functions of angular and centre-of-mass velocities, and unit vectors
of dipole moment show that a cation of small size and high charge, such as
Ni2+, forms dynamically well-defined solvation shell. Also, with decrease in the
ion-molecule distance, the mobility of solvent molecules decreases significantly
for such ions of high charge density.
Abstract: Atomic Force Microscopy (AFM) has a huge potential for exciting new applications in medicine. It has become a versatile, powerful, and indispensible technique for studying at the nanoscale, the morphological, dynamic, and biomechanical (e.g. adhesive, elastic) properties of living cells, biomolecules, and tissues under physiological conditions. This paper presents some initial results on the use of AFM in discriminating between living normal human urothelial cells (SV-HUC) and bladder tumour cells (MGH-U1) on the basis of their ultrastructure and nanomechanical properties. The results clearly demonstrate that AFM provides a nanotool to analyse and discriminate between normal and malignant bladder cells, thus revealing its diagnostic potential for bladder cancer.
Abstract: Abstract
The principal aim of this experiment was to characterise the spatial organisation of wild type (WT) helper component proteinase (HC-Pro) multifunctional protein, involved in many functions in âviral cycleâ, such as interactions between the organism & viral pathogens, through neutron reflectivity (NR). In addition, the N-terminal deletion mutant (ïN) of HC-Pro was studied.
Introduction
HC-Pro is a multifunctional protein encoded by plant viruses of the genus Potyvirus. It is involved in a number of processes, such as virus host-to-host aphid transmission, enhancement of infectivity/genome amplification, systemic cell-to-cell movement in the plant, & suppression of post-transcriptional (PTGS) and virus-induced (VIGS) gene silencing.
HC-Pro is constituted of three domains: (A) a C-terminal domain (~150 amino acids (AA)); (B) a central region (~100 â 300 AA); and (C) an N-terminal domain (~100 AA), as also confirmed by Atomic Force Microscopic measurements that we performed prior to carrying out the NR experiments. However, little is known about the structure & organisation of the domains. Any changes occuring on viral RNA binding are also not understood.
The NR experiments were performed in solutions of varying D2O contents.
Experimental methods
The NR experiments were carried out at ï± = 0.35, 0.8, & 1.8ï°, to collect 30, 60, & 120ïA, respectively. A liquid cell (Fig. 1) was used at the Au/D2O interface at different D2O contrasts for both WT and ïN HC-Pro. An inlet and outlet allowed flushing the cell with different solutions of D2O/H2O. The gold-coated silicon block was put inside the liquid cell upside down so that the Au layer was in contact with the poly(tetrafluoroethene) (PTFE) layer of the cell on which different solutions of D2O/H2O were flushed. All the experiments were performed at RT.
Two different Au-coated Si blocks were used for WT and ïN HC-Pro proteins respectively. Three different solutions, 100% D2O, a solution of D2O/H2O Au-matched, and a solution of D2O/H2O (30:70) were employed. The blocks were used to perform NR experiments on the bare Au surface (control) before coating them with the proteins.
Figure 1. Liquid cell used for NR experiments. On the PTFE layer the inlet and outlet are visible
Preliminary NR data analyses (Fig. 2) have shown some differences in the scattering data vs. Q (Ã-1) of WT and ïN HC-Pro, probably due to the absence of the N-terminal domain in the ïN HC-Pro mutant. However, further work still need to be done in terms of data analyses. In particular, the data from different contrasts will be fitted simultaneously to fully characterise the system and suitable theoretical models will be used to fit the NR data to properly understand the spatial organisation of the HC-Pro domains relative to each other.
Figure 2. Scattering data vs. Q (Ã-1) for different D2O/H2O solutions are shown. Rows (1): Control, (2): WT HC-Pro, (3) ïN HC-Pro.
Abstract: The principal aim of this proposal is to extend our ongoing international programme of work on the structural studies of molten salts by experimental (neutrons, X-rays) and modelling (MD simulations) techniques to fluoride melts, which, due to their high melting points, corrosive nature and containment problems, have so far not been investigated. Nevertheless, they are extremely important systems both technological and scientifical viewpoints. Before attempting to investigate pure lanthanide fluorides, which melt (Tm) at ~1500 °C (e.g., Tm for LaF3: 1493 °C, CeF3: 1430 °C), we have decided to first work at lower temperatures of ~900 °C by investigating the structures of LiF (Tm = 845 °C) and 0.2 LaF3 + 0.8 LiF (Tm = 780 °C) by isotopic substitution on Li (using 0Li and 7Li isotopes). This work forms a part of our systematic studies aimed at studying the effect of both the size of the cation and the anion on the structures of molten trivalent metal halides, their mixtures with alkali metalhalides, and other related compounds.
Abstract: The aims of the proposed studies were to investigate the structural phase transitions in a number of divalent and trivalent metal fluorides. The fluoride salts pose a number of problems due to the high operating temperatures and the difficulties in finding appropriate containers that would resist corrosion. After careful thoughts, tantalum containers of 60 mm height, 9 mm i. d., and 10 mm o. d were specially designed. The holders, also made from Ta, were designed to fit into the stick of the GEM furnace through M8 female screw thread (See Fig. 1).
The physico-chemical properties of inorganic metal fluorides at high temperatures still remain virtually unexplored though these materials are extremely promising for nuclear engineering, pyrochemical reprocessing, and material synthesis. Some of these fluorides show super-ionic conduction, especially in their high temperature phases. However, the exact phase transition temperatures and the mechanisms of such transitions are still unknown. From this viewpoint, we investigated the structures of (i) BaF2 (200 â 1050 ï°C), (ii) SrF2 (200 â 1185 ï°C), (iii) CaF2 (200 â 1205 ï°C), (iv) LaF3 (200 â 1420 ï°C), and (v) YF3 (200 â 1150 ï°C). Scattering measurements were also performed on the empty Ta-container at the same temperatures. Superionic transition temperatures from other measurements have been reported to be 940, 1073-1273, 1135, 1370, and 1082 ï°C, while their melting points are 1368, 1477, 1418, 1493, and 1150 ï°C, respectively, for BaF2, SrF2, CaF2, LaF3, and YF3. Using the raw scattering data, SQRAW files have been created. Some of the results are shown in Figures 2-4. With increase in temperature, the peak intensities decrease in accordance with the Debye-Waller effect, and the peaks at high-Q get shifted to lower Q-values. Following this data conversion, an OpenGenie procedure has been written and tested to create the GSAS data files from the SQRAW files.
Further comprehensive analyses of the data are in progress, and the results will be reported separately. The above work forms a part of our broader research programme [1-2] involving the joint application of multi techniques, such as XAFS, neutron diffraction, and molecular dynamics simulations, to explore the structures of fluoride materials with a view to promote their practical applications as detailed above.
References
1. H. Matsuura, S. Watanabe, T. Kanuma, H. Akatsuka, T. Honma, N. Umesaki, A. Kajinami, A. K. Adya, and R. Fujita, Physica Scripta, T115, 294, (2005).
2. S. Watanabe, A.K. Adya, et al, and H. Matsuura, J. Alloys & Compounds (2005) In the Press.
Abstract: A microscopic understanding of electrolyte solutions has long been an aim of physical chemistry and liquid-state physics. Although neutron diffraction isotopic substitution techniques have been used for the past two decades to elucidate the interatomic structure of a diversity of aqueous solutions, such studies on non-aqueous electrolyte solutions are scarce due to their very complex nature. Application of complementary techniques is often essential to determine atomic correlations not well resolved even at the neutron second-order difference level. In the following, we shall show how the application of ab initio quantum chemical calculations and molecular mechanics modelling in conjunction with isotopic substitution experiments have helped us to resolve microscopic structural details of ion-solvation shells in solutions of NiCl2 in methanol.
