Protein purification using anion exchange membranes Term Paper

Protein purification using anion exchange membranes - Term Paper Example This change results in the protein being less capable of forming a strong ionic interaction with negatively charged cation exchanger. A similar chain of events occurs with anion exchange media. At a lower pH of the mobile phase the target molecule becomes more protonated and hence positively charged. The result is that the target molecule no longer has the capability to form a strong ionic interaction with the positively charged anion exchanger which causes the molecule to elute from stationary phase. Ion exchange is the most commonly practiced chromatographic method of protein purification due to its ease. This technique exploits the amphoteric character of a protein ( net positive in low pH buffer and negative in a high pH buffer). The technique exploits the fact that the distribution and net charge on the protein’s surface determines the interaction of the protein with the charged groups on the surface of the immobile phase, an anion exchange membrane in this case. The char ges on the protein and the membrane must be opposite for the exchange interaction to occur. The support membrane, which has covalently attached positive functional groups, is referred to as an anion exchanger if mobile negatively charged anions will be the exchanged species. ... In membrane chromatographic processes, the transport of solutes to their binding sites take place predominantly by convection and the pore diffusion is very small comparing with the beads column, thereby the mass transfer resistance is tremendously reduced. Membrane chromatography is a promising process for the isolation, purification, and recovery of proteins, enzymes, and nuclear acids. Comparing with traditional beads column chromatography, membrane chromatography can be faster, easier and cheaper to mass-produce. And also, it is easy to set up and scale up. Most important is saving time in membrane chromatography, this is important because many proteins lose their activities with time. Membranes are also more convenient because they do not require column hardware or packing, they reduce buffer usage and floor space requirements and they generally improve manufacturing flexibility. There are mainly three shapes of membrane available, including flat sheet, hollow fiber and radial f low used for protein purification (2). (From http://www.natrixseparations.com/media/application_note7.pdf) Figure 1 Principles of an anion exchange chromatography: Lowering pH on the protein elution from positively charged anion-exchange membrane. Molecules with higher charge density bind much stronger to the membrane and consequently require greater change in pH to be released from the membrane surface. Theory: Proteins are bound to anion exchange membranes by reversible, electrostatic interactions. A separation is obtained because the diverse array of molecular species have different affinities for the exchanger. The adsorbed proteins are eluted in order of least to most strongly bound molecules,

Interview with a HR Director Essay Example | Topics and Well Written Essays - 750 words

Interview with a HR Director - Essay Example Why I chose to interview an HR Director? People generally confuse HR Directors with HR Managers, and do not generally know the exact responsibilities of each of the two, and more precisely, the HR Director in the HR department of an organization. HR Director is also not talked about as frequently as HR Managers in the discussions of various HR professionals. I personally consulted a lot of resources to learn about the work of an HR Director. However, every time I tried, I got to listen or read about an HR Manager. Discussion about an HR Director is not as abundant as that of other HR professionals. Therefore, I considered interviewing an HR Director so that I could both enhance my personal understanding of an HR Director’s job, and share the information with others to enhance their knowledge about an HR Director. Questions of the interview: frequently used by an HR Director? ... 12. Although HR Director fundamentally assumes the role of a leader for the HR department, yet he/she also has to be a very good Manager to do the job perfectly, agree? 13. Where is the interface between leadership and management? 14. What HR roles, other than HR Director, have you played in your professional career so far? 15. How have those roles influenced your capabilities as an HR Director? 16. Is it recommendable for an individual to start directly from an HR Director’s post without a former experience in lower level HR jobs? The learning I gained: The fundamental responsibility of an HR Director is to monitor the activities of all the organization’s divisions. The HR Director communicates with the top management and devised strategies so as to enhance the organizational policies, practices and procedures as per the changing demands of the growing business and the altering business environment. An HR Director interviews employees, trains new workers, decides pay r ates for different employees, and prepares organizational benefit plans. The HR Director also balances the general ledger (Jeffress). Occasionally, an HR Director may study the system of other organizations with a view to determining the competitive salaries and wages, and developing a modified and improvised recruiting campaign for hiring talented employees for the organization. In small scale businesses, the HR Directors frequently meet with the workers to learn their individualistic and collective concerns and resolve their issues to improve their performance. On the other hand, in large scale businesses, the duties of HR are distributed between different departments in order to achieve accuracy in work and make it