Raman Scattering:From Structural Biology to Medical Applications

This is a review of relevant Raman spectroscopy (RS) techniques and their use in structural biology, biophysics, cells, and tissues imaging towards development of various medical diagnostic tools, drug design, and other medical applications. Classical and contemporary structural studies of different water-soluble and membrane proteins, DNA, RNA, and their interactions and behavior in different systems were analyzed in terms of applicability of RS techniques and their complementarity to other corresponding methods. We show that RS is a powerful method that links the fundamental structural biology and its medical applications in cancer, cardiovascular, neurodegenerative, atherosclerotic, and other diseases. In particular, the key roles of RS in modern technologies of structure-based drug design are the detection and imaging of membrane protein microcrystals with the help of coherent anti-Stokes Raman scattering (CARS), which would help to further the development of protein structural crystallography and would result in a number of novel high-resolution structures of membrane proteins—drug targets; and, structural studies of photoactive membrane proteins (rhodopsins, photoreceptors, etc.) for the development of new optogenetic tools. Physical background and biomedical applications of spontaneous, stimulated, resonant, and surface- and tip-enhanced RS are also discussed. All of these techniques have been extensively developed during recent several decades. A number of interesting applications of CARS, resonant, and surface-enhanced Raman spectroscopy methods are also discussed

Pair-breaking quantum phase transition in superconducting nanowires

A quantum phase transition (QPT) between distinct ground states of matter is a wide-spread phenomenon in nature, yet there are only a few experimentally accessible systems where the microscopic mechanism of the transition can be tested and understood. These cases are unique and form the experimentally established foundation for our understanding of quantum critical phenomena. Here we report the discovery that a magnetic-field-driven QPT in superconducting nanowires - a prototypical 1d-system - can be fully explained by the critical theory of pair-breaking transitions characterized by a correlation length exponent $\nu \approx 1$ and dynamic critical exponent $z \approx 2$. We find that in the quantum critical regime, the electrical conductivity is in agreement with a theoretically predicted scaling function and, moreover, that the theory quantitatively describes the dependence of conductivity on the critical temperature, field magnitude and orientation, nanowire cross sectional area, and microscopic parameters of the nanowire material. At the critical field, the conductivity follows a $T^{(d-2)/z}$ dependence predicted by phenomenological scaling theories and more recently obtained within a holographic framework. Our work uncovers the microscopic processes governing the transition: The pair-breaking effect of the magnetic field on interacting Cooper pairs overdamped by their coupling to electronic degrees of freedom. It also reveals the universal character of continuous quantum phase transitions.Comment: 22 pages, 5 figure

Software especial para calcular las funciones especiales de catástrofes de olas

The method of ordinary differential equations in the context of calculating the special functions of wave catastrophes is considered. Complementary numerical methods and algorithms are described. The paper shows approaches to accelerate such calculations using capabilities of modern computing systems. Methods for calculating the special functions of wave catastrophes are considered in the framework of parallel computing and distributed systems. The paper covers the development process of special software for calculating of special functions, questions of portability, extensibility and interoperability.Se considera el método de ecuaciones diferenciales ordinarias ordinarias en el contexto de calcular funciones especiales de catástrofes de olas. Se describen métodos y algoritmos numéricos complementarios. El artículo muestra enfoques para acelerar tales cálculos usando capacidades modernas de sistemas de cálculo. Se consideran métodos para calcular funciones especiales de catástrofes de olas en el marco de computación en paralelo y sistemas distribuidos. El artículo cubre el proceso de desarrollo de software especial para calcular funciones especiales, así como asuntos de portabilidad, extensibilidad e interoperabilidad

Special software for computing the special functions of wave catastrophes

Se considera el método de ecuaciones diferenciales ordinarias ordinarias en el contexto de calcular funciones especiales de catástrofes de olas. Se describen métodos y algoritmos numéricos complementarios. El artículo muestra enfoques para acelerar tales cálculos usando capacidades modernas de sistemas de cálculo. Se consideran métodos para calcular funciones especiales de catástrofes de olas en el marco de computación en paralelo y sistemas distribuidos. El artículo cubre el proceso de desarrollo de software especial para calcular funciones especiales, así como asuntos de portabilidad, extensibilidad e interoperabilidad.The method of ordinary differential equations in the context of calculating the special functions of wave catastrophes is considered. Complementary numerical methods and algorithms are described. The paper shows approaches to accelerate such calculations using capabilities of modern computing systems. Methods for calculating the special functions of wave catastrophes are considered in the framework of parallel computing and distributed systems. The paper covers the development process of special software for calculating of special functions, questions of portability, extensibility and interoperability

TiAl-Based Materials by In Situ Selective Laser Melting of Ti/Al Reactive Composites

Additive manufacturing (AM) of refractory materials requires either a high laser power or the use of various easily melting binders. In this work, we propose an alternative—the use of spherical reactive Ti/Al composite particles, obtained by preliminary high-energy ball milling. These powders were used to produce high-temperature TiAl-based materials during the selective laser melting (SLM) process. When laser heating is applied, mechanically activated composite particles readily react with the release of a considerable amount of heat and transform into corresponding intermetallic compounds. The combustion can be initiated at relatively low temperatures, and the exothermic effect prevents the sharp cooling of as-sintered tracks. This approach allows one to produce dense intermetallic materials with a homogeneous structure in one step via SLM and eliminates the need for powerful lasers, binders, or additional post-processing and heat treatments

Changes in Amino Acid and Acylcarnitine Plasma Profiles for Distinguishing Patients with Multiple Sclerosis from Healthy Controls

McDonald criteria and magnetic resonance imaging (MRI) are used for the diagnosis of multiple sclerosis (MS); nevertheless, it takes a considerable amount of time to make a clinical decision. Amino acid and fatty acid metabolic pathways are disturbed in MS, and this information could be useful for diagnosis. The aim of our study was to find changes in amino acid and acylcarnitine plasma profiles for distinguishing patients with multiple sclerosis from healthy controls. We have applied a targeted metabolomics approach based on tandem mass-spectrometric analysis of amino acids and acylcarnitines in dried plasma spots followed by multivariate statistical analysis for discovery of differences between MS (n=16) and control (n=12) groups. It was found that partial least square discriminant analysis yielded better group classification as compared to principal component linear discriminant analysis and the random forest algorithm. All the three models detected noticeable changes in the amino acid and acylcarnitine profiles in the MS group relative to the control group. Our results hold promise for further development of the clinical decision support system

Silicon in a Negatively Charged Shell: Anions of Spirosilabifluorene

Mono- and dianions of a polycyclic compound with a central sp³-hybridized silicon atom, spirosilabifluorene (C₂₄H₁₆Si, <b>1</b>), were prepared by reduction with alkali metals. The salts containing <b>1</b>^•– and <b>1</b>^2– anions were isolated and studied by single-crystal X-ray diffraction. The lithium salt of the C₂₄H₁₆Si^•– radical monoanion ([Li­(THF)₄⁺]­[<b>1</b>^•–], <b>2</b>) exists as a solvent-separated ion pair in the solid state. Substantially different geometrical parameters were found for each of the fluorene groups within the C₂₄H₁₆Si^•– anion of <b>2</b> due to asymmetric charge distribution. The C₂₄H₁₆Si^2– dianion was isolated in the form of its sodium ([{Na­(THF)₃⁺}­{Na­(THF)⁺(<b>1</b>^2–)], <b>3</b>) or potassium ([{K­(THF)⁺}₂(<b>1</b>^2–)], <b>4</b>) salt. The environment at the central silicon atom in the dianion is flattened in comparison to the monoanion and neutral compound, with the angle between the two fluorene planes measured at 55° in <b>1</b>^2– vs 89<b>°</b> in <b>1</b>^•– and 83° in <b>1</b>⁰. The aggregation of dianions and alkali-metal counterions leads to the formation of dimeric units and 1D polymeric chains in the solid sodium and potassium salts, respectively. The structure of the cesium salt <b>5</b>, containing both mono- and dianions in the crystal lattice, was also studied by X-ray diffraction. Complexes <b>2</b>–<b>5</b> were investigated by ESR and variable-temperature multinuclear NMR spectroscopy. Theoretical investigations at the PBE0, MP2, and multireference NEVPT2 levels of theory for the C₂₄H₁₆Si^<i>n</i>– (<i>n</i> = 0–2) species revealed the conjugation of two fluorene units over the central silicon atom and a singlet ground state for the dianion

Silicon in a Negatively Charged Shell: Anions of Spirosilabifluorene

Mono- and dianions of a polycyclic compound with a central sp³-hybridized silicon atom, spirosilabifluorene (C₂₄H₁₆Si, <b>1</b>), were prepared by reduction with alkali metals. The salts containing <b>1</b>^•– and <b>1</b>^2– anions were isolated and studied by single-crystal X-ray diffraction. The lithium salt of the C₂₄H₁₆Si^•– radical monoanion ([Li­(THF)₄⁺]­[<b>1</b>^•–], <b>2</b>) exists as a solvent-separated ion pair in the solid state. Substantially different geometrical parameters were found for each of the fluorene groups within the C₂₄H₁₆Si^•– anion of <b>2</b> due to asymmetric charge distribution. The C₂₄H₁₆Si^2– dianion was isolated in the form of its sodium ([{Na­(THF)₃⁺}­{Na­(THF)⁺(<b>1</b>^2–)], <b>3</b>) or potassium ([{K­(THF)⁺}₂(<b>1</b>^2–)], <b>4</b>) salt. The environment at the central silicon atom in the dianion is flattened in comparison to the monoanion and neutral compound, with the angle between the two fluorene planes measured at 55° in <b>1</b>^2– vs 89<b>°</b> in <b>1</b>^•– and 83° in <b>1</b>⁰. The aggregation of dianions and alkali-metal counterions leads to the formation of dimeric units and 1D polymeric chains in the solid sodium and potassium salts, respectively. The structure of the cesium salt <b>5</b>, containing both mono- and dianions in the crystal lattice, was also studied by X-ray diffraction. Complexes <b>2</b>–<b>5</b> were investigated by ESR and variable-temperature multinuclear NMR spectroscopy. Theoretical investigations at the PBE0, MP2, and multireference NEVPT2 levels of theory for the C₂₄H₁₆Si^<i>n</i>– (<i>n</i> = 0–2) species revealed the conjugation of two fluorene units over the central silicon atom and a singlet ground state for the dianion

Tuning the separation and coupling of corannulene trianion-radicals through sizable alkali metal belts

International audienceThe first heterobimetallic sandwich-type aggregate formed by bowl-shaped corannulene trianion-radicals,C20H10c3-, has been synthesized using mixed-metal reduction of C20H10. The product was crystallographically characterized to reveal the self-assembly of [Cs+//(C20H10.3-)/4K+/(C20H10 3-)//Cs+], in which two triply-charged corannulene decks encapsulate a rectangle of four potassium ions (the K/K separations are 4.212(4) and 5.185(4) °A), with the exterior concave bowl cavities being selectively filled by one cesium ion each. In order to provide insights into the geometrical features and electronic structure of this novel mixed-metal organometallic self-assembly, an in-depth theoretical investigation has been carried out..