Structural Biochemistry/Lipids/Techniques to Study Membranes/Scanning Calorimetry
Scanning Calorimetry is a technique used to study phase transitions in lipids as well as proteins and other non-organic systems. The basic idea of scanning calorimetry is the use of two cells one containing a buffer of known specific heat and the other to be studied. In scanning calorimetry, heat is added to both cells while the temperature of both are being recorded. When temperature differences occur, the calorimeter understands to add heat to one of the cells so that the temperature in both cells are always equal. The scanning part comes from the constant scanning/measurement of temperature and heat, dependent on time. As the cell being studied reaches a phase transition, it will begin to need much more heat to raise the temperature of the studied cell to that of the sample cell.
Applications in Biochemistry
Scanning calorimetry can be used to study the melting temperature,Tm of proteins and lipids. By using the same principles as mentioned in the overview, it can be determined when a protein is becoming denatured. Also when equations of enthalpy and Gibbs free energy are combined with calorimetry, the relative amounts and specific heats of proteins, lipids, and other macromolecules can be determined. Scanning calorimetry has allowed scientists to elucidate structures and interacts occurring in macromolecules quantitatively, that otherwise would not be known. Such values as stability in native form can be measured by Scanning calorimetry, by using the equation change in G=-RT(lnK) where G is the gibbs free energy, R is the gas constant, T is the temperature in Kelvin, and K is the equilibrium constant.
Scanning calorimetry can be effectively applied to study phase shifts. When a solid enters a liquid phase it is not simply a discrete transformation but rather one with a transition state and a gradual process involving kinetics atom arrangement. The state that is occupied between a solid and a liquid is called the mesomorphous state and by using scanning calorimetry we can observe energy changes in a given period of time and relate that energy change to how rapidly or slowly the atoms are dispersing and rearranging themselves.
Using an airtight chamber scanning calorimetry can be used to determine measures of storing a certain compound or the chemical conditions necessary for a successful procedure or investigation. Oxidative tests using nitrogen can be added to a system with the compound of interest. If oxidation occurs and depending on the rate and we can readily identify if one condition is suitable or not suitable to store a sensitive compound. Therefore scanning calorimetry makes a good safety tool. By studying an exothermic event and assessing the stability of a certain compound in different amounts of heat scanning calorimetry can tell us the maxium temperature of the material and its characteristics of its micro chemistry under heat.
Polymers are often broken down to identify different parts of their composition. Scanning calorimetry can check the composition using databases and compilations of standards. Scanning calorimetry of individual substituents can help identify parts of complex polymers that we find the future. By degrading a polymer we can also investigate the heat and exothermic character once again and then we can tell what the composition is made of. Scanning calorimetry also provides graphs that can show crystallization peaks which can tell us the percentage of crystallinity which will give us insight on polymer purities and freezing point depression. And of course this can be applied to medicine because scanning calorimetry can assess what temperature to process a drug so the drug does not crystallize and become untakeable. Also cross linking of polymers is common in polymer industries and each time polymers do so, scanning calorimetry can provide a graph curve to show the time of transition and that can be further evaluated.