SDS PAGE Term Paper Example | Topics and Well Written Essays - 750 words

SDS PAGE - Term Paper Example -mecaptoethamol prevents oxidation of cysteines and break up disulphide bonds, Bromophenyl dye is used to help in visualizing the sample as it travels across the gel and glycerol is added to make the sample fall to the bottom. (Leamlli, 1970). Electric charge is applied across the gel to influence the movement of protein molecules to positively charged end. Principal behind SDS PAGE The structure of protein molecules to be separated has portions of negative and positive charges resulting from charged R-groups of particular amino acid and hydrophobic portions of nonpolar R-groups hence difference in shapes and sizes of protein molecules. (Hempelmann, 2008) Therefore, the first stage of SDS PAGE is to make the protein molecules linear and to ensure that there are no secondary, tertiary, or quaternary molecular structures in the sample. This is achieved by injecting the sample with SDS, which is a detergent that can dissolve the membrane and solubilise the protein molecules. Its negativ e charge overcome positive charges of protein molecules. The resulting protein is denatured, linearized, and negatively charged. The next stage in SDS PAGE is the separation process. This is based on the molecular size and weight of the molecules, sieving properties of the gel is of great assistance at this stage since protein molecules have the same charge-to-mass-ratio. The gel is not a solid but made up of series of tunnel of different diameters running from one end to the other and are scattered through the gel. (SDS PAGE, 2009) Velocity of particles moving through an electric field is directly proportional to strength of the electric field and degree of charge in the particle but inversely proportional to size of the particles and viscosity of the medium. This is the basis upon which protein of different sizes are separated. (SDS PAGE. 2009). The discontinuous pH parts of the gel come handy in aligning the proteins properly at the starting point. Laemmli gel is composed of stac ker and running gel, the running gel is buffed with Tris to pH of 8.8 with HCl; stacker gel is adjusted with Tris to pH 6.8 with HCl. The electrode buffer is adjusted to pH 8.3 using glycine and the gel is then run at a constant voltage. (Leamlli, 1970) When the power is switched on, glycine (which is a weak acid and can exist in an uncharged state as zwitterions at low pH, or in a charged state as glycinate anion at high pH) ions in the running buffer wants to move away from the negative electrode towards the sample and the stacking gel. The pH in stacking gel is low and so glycin ions lose their charge and slow down. In the stacker and sample, negatively charged mobile chloride ions move away from the cathode creating a narrow zone of very low conductance (very high electrical resistance) in the top of the stacking gel. Almost all the applied voltage is concentrated in this small zone. The very high field strength makes the negatively charged proteins to move forward. The trick, h owever, is that they can never outrun the chloride ions. If they did, they would find themselves in a region of high conductance and very low field strength and would immediately slow down. The result is that all the proteins move through the stacker in a tight

Risk Behavior in Youth Essay Example | Topics and Well Written Essays - 2500 words

Risk Behavior in Youth - Essay Example Most of the established studies on young people in Western societies have been devoted to an understanding of their transition within their families and schools towards adulthood and their working lives. During the different stages of their transition, the young people confront or create risks as they go through. Risk behaviours that include tobacco, alcohol, and drug use are common in young adults, and it is a common finding that those who engage in risky behaviours are prone to engage in additional risky behaviours with passage of time. Social sciences have established that as the number of risky behaviours increase, depression as a comorbidity emerges that take away the productive and fruitful time out of the youth (Viner, R. and Macfarlane, A., 2000). Although not universally true, the young people are prone to take risks sometimes to the extent of a risky life. More recent research in Europe, the UK, the US, and Australia demonstrate a out of bound mismatch between the conventio nal models of transition and the attitudes, choices, and experience of young people themselves in reality. The reason may be significant social and economic changes since the early 1970s. These could have introduced elements of uncertainty, unpredictability and risk into the lives of the young (Young, R., Beinum, MV., Sweeting, H., and West, P., 2007). Thus, it can be stated that risk is a useful concept in understanding young people. In the following sections, evidence for that would be analysed in order to find support for this statement, so some solution can be found to prevent this. Endemicity of Risk There is evidence that risk and uncertainty are certainly endemic, and technology and social institutions are unable to eliminate it. The modern notion of risk is guided largely by uncertainty. Harvest failure, pestilence, migrations, new currents in religion, technological developments, and the unforeseen consequences of urbanization have all exerted a powerful and typically unpredicted influence on the problems and difficulties the population including the young face (Case, S., 2006). Traditionally, lack of certainty in life was attributed to "the other" agencies beyond human control: the ignorance of imperfect humanity, divine agency, luck, destiny, or fate. Many events in the history of society have been the eye openers of the fact that risk has accompanied technical development and revealed the weaknesses of institutions for managing the resulting uncertainty. The social scientific study of people's responses to risk tends to focus on either their narrow cognitive or their broad sociocultural roots (Dworkin, J., 2005). The Young There is a diversity of experiences that characterises the lives of the young people. Although they belong to the same generation they have emerged with different aspirations for the future and have made different choices about their personal interests and priorities, and hence they have different life patterns that do not match with any linear assumption or prediction. Research has shown that young people do indeed possess a sense of persistence and determination in the face of frustrated expectations. After education, every