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Isothermal Titration Calorimetry
Isothermal titration calorimetry (ITC) is a physical technique used to determine the thermodynamic parameters of interactions in solution. It is most often used to study the binding of small molecules (such as medicinal compounds) to larger macromolecules (proteins, DNA etc.). It consists of two cells which are enclosed in an adiabatic jacket. The compounds to be studied are placed in the sample cell, while the other cell, the reference cell, is used as a control and contains the buffer in which the sample is dissolved. Thermodynamic measurements ITC is a quantitative technique that can determine the binding affinity (K_a), enthalpy changes (\Delta H), and binding stoichiometry (n) of the interaction between two or more molecules in solution. From these initial measurements, Gibbs free energy changes (\Delta G) and entropy changes (\Delta S) can be determined using the relationship: :::\Delta G = -RT\ln = \Delta H -T\Delta S (where R is the gas constant and T is the absolute ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermal Analysis
Thermal analysis is a branch of materials science where the properties of materials are studied as they change with temperature. Several methods are commonly used – these are distinguished from one another by the property which is measured: * Dielectric thermal analysis: dielectric permittivity and loss factor * Differential thermal analysis: temperature difference versus temperature or time * Differential scanning calorimetry: heat flow changes versus temperature or time * Dilatometer, Dilatometry: volume changes with temperature change * Dynamic mechanical analysis: measures storage modulus (stiffness) and loss modulus (damping) versus temperature, time and frequency * Evolved gas analysis: analysis of gases evolved during heating of a material, usually decomposition products * Isothermal titration calorimetry * Isothermal microcalorimetry * Laser flash analysis: thermal diffusivity and thermal conductivity * Thermogravimetric analysis: mass change versus temperature or time ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Association Constant
The binding constant, or affinity constant/association constant, is a special case of the equilibrium constant ''K'', and is the inverse of the dissociation constant. It is associated with the binding and unbinding reaction of receptor (R) and ligand (L) molecules, which is formalized as: :R + L RL The reaction is characterized by the on-rate constant ''k''on and the off-rate constant ''k''off, which have units of M−1 s−1 and s−1, respectively. In equilibrium, the forward binding transition R + L → RL should be balanced by the backward unbinding transition RL → R + L. That is, :k_\,[]\,[] = k_\,[], where [R], [L] and [RL] represent the concentration of unbound free receptors, the concentration of unbound free ligand and the concentration of receptor-ligand complexes. The binding constant ''K''a is defined by :K_ = = . An often considered quantity is the dissociation constant ''K''d ≡ , which has the unit of concentration, despite the fact that str ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biophysics
Biophysics is an interdisciplinary science that applies approaches and methods traditionally used in physics to study biological phenomena. Biophysics covers all scales of biological organization, from molecular to organismic and populations. Biophysical research shares significant overlap with biochemistry, molecular biology, physical chemistry, physiology, nanotechnology, bioengineering, computational biology, biomechanics, developmental biology and systems biology. The term ''biophysics'' was originally introduced by Karl Pearson in 1892.Roland Glaser. Biophysics: An Introduction'. Springer; 23 April 2012. . The term ''biophysics'' is also regularly used in academia to indicate the study of the physical quantities (e.g. electric current, temperature, stress, entropy) in biological systems. Other biological sciences also perform research on the biophysical properties of living organisms including molecular biology, cell biology, chemical biology, and biochemistry. Overview ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biochemistry Methods
The following outline is provided as an overview of and topical guide to biochemistry: Biochemistry – study of chemical processes in living organisms, including living matter. Biochemistry governs all living organisms and living processes. Applications of biochemistry * Testing ** Ames test – salmonella bacteria is exposed to a chemical under question (a food additive, for example), and changes in the way the bacteria grows are measured. This test is useful for screening chemicals to see if they mutate the structure of DNA and by extension identifying their potential to cause cancer in humans. ** Pregnancy test – one uses a urine sample and the other a blood sample. Both detect the presence of the hormone human chorionic gonadotropin (hCG). This hormone is produced by the placenta shortly after implantation of the embryo into the uterine walls and accumulates. ** Breast cancer screening – identification of risk by testing for mutations in two genes&md ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scientific Techniques
A scientific technique is any systematic way of obtaining information about a scientific nature or to obtain a desired material or product. Scientific techniques can be divided in many different groups, e.g.: # Preparative techniques ## Synthesis techniques, e.g. the use of Grignard reagents in organic chemistry ## Growth techniques, e.g. crystal growth or cell cultures in biology ## Purification techniques e.g. those in chemistry # Measurement techniques ## Analysis techniques, e.g. ones that reveal atomic or molecular composition. ## Characterization techniques, e.g. ones that measure a certain property of a material. ## Imaging techniques, e.g. microscopy In some cases these methods have evolved into instrumental techniques that require expensive equipment. This is particularly true in sciences like physics, chemistry, and astronomy. It is customary to abbreviate the names of techniques into acronyms, although this does not hold for all of them. Particularly the advent of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Surface Plasmon Resonance
Surface plasmon resonance (SPR) is the resonant oscillation of conduction electrons at the interface between negative and positive permittivity material in a particle stimulated by incident light. SPR is the basis of many standard tools for measuring adsorption of material onto planar metal (typically gold or silver) surfaces or onto the surface of metal nanoparticles. It is the fundamental principle behind many color-based biosensor applications and lab-on-a-chip sensors. It should be stressed that SPR is not a resonance on the planar surface and it is a polariton or surface-wave like phenomenon. Explanation The surface plasmon polariton is a non-radiative electromagnetic surface wave that propagates in a direction parallel to the negative permittivity/dielectric material interface. Since the wave is on the boundary of the conductor and the external medium (air, water or vacuum for example), these oscillations are very sensitive to any change of this boundary, such as the adso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pressure Perturbation Calorimetry
Pressure perturbation calorimetry (PPC) is a technique closely related to isothermal titration calorimetry (ITC) and differential scanning calorimetry (DSC). In brief, PPC measures heat changes associated with dilute aqueous solutions of proteins or other biomolecules in response to introduction of relatively small pressure perturbations (± 5 atm). Importantly, such heat changes can be related to thermodynamic properties of proteins such as hydration and conformational transitions upon folding and/or ligand binding. See also * Differential scanning calorimetry * Isothermal microcalorimetry * Isothermal titration calorimetry Isothermal titration calorimetry (ITC) is a physical technique used to determine the thermodynamic parameters of interactions in solution. It is most often used to study the binding of small molecules (such as medicinal compounds) to larger macro ... * Sorption calorimetry Bibliography * * * {{refend Calorimetry ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sorption Calorimetry
The method of sorption calorimetry is designed for studies of hydration of complex organic and biological materials. It has been applied for studies of surfactants, lipids, DNA, nanomaterials and other substances. A sorption calorimetric experiment is performed at isothermal regime, but different temperatures can be studied in separate experiments. In a sorption calorimetric experiment, a two-chamber calorimetric cell is inserted into a double-twin microcalorimeter. Water evaporates, diffuses through the tube connecting two chambers of the calorimetric cell and is absorbed by the studied substance. The amount of evaporated water is calculated from the thermal power registered in the vaporisation chamber: :n_w= \frac From the same data, the activity of water in the sample can also be calculated: :a_w=1-\frac From the thermal powers registered in the two chambers one can calculate the partial molar enthalpy of mixing of water. During the sorption experiment the water content ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dual Polarisation Interferometry
Dual-polarization interferometry (DPI) is an analytical technique that probes molecular layers adsorbed to the surface of a waveguide using the evanescent wave of a laser beam. It is used to measure the conformational change in proteins, or other biomolecules, as they function (referred to as the conformation activity relationship). Instrumentation DPI focuses laser light into two waveguides. One of these functions as the "sensing" waveguide having an exposed surface while the second one functions to maintain a reference beam. A two-dimensional interference pattern is formed in the far field by combining the light passing through the two waveguides. The DPI technique rotates the polarization of the laser, to alternately excite two polarization modes of the waveguides. Measurement of the interferogram for both polarizations allows both the refractive index and the thickness of the adsorbed layer to be calculated. The polarization can be switched rapidly, allowing real-time measur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Endothermic
In thermochemistry, an endothermic process () is any thermodynamic process with an increase in the enthalpy (or internal energy ) of the system.Oxtoby, D. W; Gillis, H.P., Butler, L. J. (2015).''Principle of Modern Chemistry'', Brooks Cole. p. 617. In such a process, a closed system usually absorbs thermal energy from its surroundings, which is heat transfer into the system. Thus, an endothermic reaction generally leads to an increase in the temperature of the system and a decrease in that of the surroundings. It may be a chemical process, such as dissolving ammonium nitrate () in water (), or a physical process, such as the melting of ice cubes. The term was coined by 19th-century French chemist Marcellin Berthelot. The opposite of an endothermic process is an exothermic process, one that releases or "gives out" energy, usually in the form of heat and sometimes as electrical energy. Thus in each term (endothermic and exothermic) the prefix refers to where heat (or electrical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ligand
In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electron pairs, often through Lewis bases. The nature of metal–ligand bonding can range from covalent to ionic. Furthermore, the metal–ligand bond order can range from one to three. Ligands are viewed as Lewis bases, although rare cases are known to involve Lewis acidic "ligands". Metals and metalloids are bound to ligands in almost all circumstances, although gaseous "naked" metal ions can be generated in a high vacuum. Ligands in a complex dictate the reactivity of the central atom, including ligand substitution rates, the reactivity of the ligands themselves, and redox. Ligand selection requires critical consideration in many practical areas, including bioinorganic and medicinal chemistry, homogeneous catalysis, and environmental chemi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exothermic
In thermodynamics, an exothermic process () is a thermodynamic process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity (e.g. a battery), or sound (e.g. explosion heard when burning hydrogen). The term ''exothermic'' was first coined by 19th-century French chemist Marcellin Berthelot. The opposite of an exothermic process is an endothermic process, one that absorbs energy usually in the form of heat. The concept is frequently applied in the physical sciences to chemical reactions where chemical bond energy is converted to thermal energy (heat). Two types of chemical reactions Exothermic and endothermic describe two types of chemical reactions or systems found in nature, as follows: Exothermic After an exothermic reaction, more energy has been released to the surroundings than was absorbed to initiate and maintain the reaction. An example would be the burn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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