Sunday, December 29, 2019

Phosphate-Buffered Saline or PBS Solution

PBS or phosphate-buffered saline is a buffer solution that is particularly valuable because it mimic the ion concentration, osmolarity, and pH of human body fluids. In other words, its isotonic to human solutions, so its less likely to cause cell damage, toxicity,  or unwanted precipitation in biological, medical, or biochemical research. PBS Chemical Composition There are several recipes to prepare PBS solution. The essential solution contains water, sodium hydrogen phosphate, and sodium chloride. Some preparations contain potassium chloride and potassium dihydrogen phosphate. EDTA may also be added in cellular preparation to prevent clumping. Phosphate-buffered saline is not ideal for use in solutions that contain divalent cations (Fe2, Zn2) because precipitation may  occur. However, some PBS solutions do contain calcium or magnesium. Also, keep in mind phosphate may inhibit enzymatic reactions. Be particularly aware of this potential disadvantage when working with DNA. While PBS is excellent for physiological science, be aware the phosphate in a PBS-buffered sample may precipitate if the sample is mixed with ethanol. A typical chemical composition of 1X PBS has a final concentration of  10 mM PO43−, 137 mM NaCl, and 2.7 mM KCl. Heres the final concentration of reagents in the solution: Salt Concentration (mmol/L) Concentration (g/L) NaCl 137 8.0 KCl 2.7 0.2 Na2HPO4 10 1.42 KH2PO4 1.8 0.24 Protocol  for Making Phosphate-Buffered Saline Depending on your purpose, you may prepare 1X, 5X, or 10X PBS. Many people simply purchase PBS buffer tablets, dissolve them in distilled water, and adjust the pH as needed with hydrochloric acid or sodium hydroxide. However, its easy to make the solution from scratch. Here are recipes for 1X and 10X phosphate-buffered saline: Reagent Amountto add (1Ãâ€") Final concentration (1Ãâ€") Amount to add (10Ãâ€") Final concentration (10Ãâ€") NaCl 8 g 137 mM 80 g 1.37 M KCl 0.2 g 2.7 mM 2 g 27 mM Na2HPO4 1.44 g 10 mM 14.4 g 100 mM KH2PO4 0.24 g 1.8 mM 2.4 g 18 mM Optional: CaCl2†¢2H2O 0.133 g 1 mM 1.33 g 10 mM MgCl2†¢6H2O 0.10 g 0.5 mM 1.0 g 5 mM Dissolve the reagent salts in 800 ml distilled water.Adjust the pH to the desired level with hydrochloric acid. Usually this is 7.4 or 7.2. Use a pH meter to measure the pH, not pH paper or other imprecise technique.Add distilled water to achieve a final volume of 1 liter. Sterilization and Storage of PBS Solution Sterilization isnt necessary for some applications, but if your are sterilizing it, dispense the solution into aliquots and autoclave for 20 minutes at 15 psi (1.05 kg/cm2) or use filter sterilization. Phosphate-buffered saline may be stored at room temperature. It may also be refrigerated, but 5X and 10X solution may precipitate when cooled. If you must chill a concentrated solution, first store it at room temperature until you are certain the salts have completely dissolved. If precipitation does occur, warming the temperature will bring them back into solution. Shelf life of refrigerated solution is 1 month. Diluting a 10X Solution to Make 1X PBS 10X is a concentrated or stock solution, which may be diluted to make a 1X or normal solution. A 5X solution must be diluted 5 times to make a normal dilution, while a 10X solution must be diluted 10 times. To prepare a 1 liter working solution of 1X PBS from a 10X PBS solution, add 100 ml of the 10X solution to 900 ml of water. This only changes the concentration of the solution, not the gram or molar amount of the reagents. The pH should be unaffected.   PBS Versus DPBS Another popular buffer solution is Dulbeccos phosphate buffered saline or DPBS. DPBS, like PBS, is used for biological research and buffers in the 7.2 to 7.6 pH range. It can be stored at room temperature. Dulbeccos solution contains a lower concentration of phosphate. It is 8.1 mM mM phosphate ions, while regular PBS is 10 mM phosphate.  The recipe for 1x DPBS is: Reagent Amount to add (1x) NaCl 8.007 g KCl 0.201 g Na2HPO4 1.150 g KH2PO4 0.200 g Optional: CaCl2†¢2H2O 0.133 g MgCl2†¢6H2O 0.102 g Dissolve the salts in 800 mL of water. Adjust pH to 7.2 to 76 using hydrochloric acid. Adjust the final volume to 1000 mL with water. Autoclave at 121 °C for 20 minutes. Sources Dulbecco, R.; et al. (1954). Plaque formation and isolation of pure lines with poliomyelitis viruses. J. Exp. Med. 99 (2): 167–182.Phosphate-buffered saline (PBS. Cold Spring Harbor Protocols (2006). Cold Spring Harbor Laboratory Press.

Saturday, December 21, 2019

People Will Do Anything For Power - 1303 Words

People will do anything for power. All over the world there are many different types of power. Some countries have presidents, some have kings and queens, and some have gods. Julius Caesar was a man that loves power. He loved thinking of himself above everyone else, and everyone else adored him. The towns people cheered for him and decorated the streets with his name. What Caesar didn’t know was that there are some people that didn’t want him to come to power, and some of them might just be the Roman Tribunes. A Tribune was a Roman official whose job was to protect the people against oppression by the patricians or nobles. The word tribune is connected to the word tribe. In Latin the word for Tribune was tribunus, which means an officer connected with a tribe, or someone that represented a tribe for specific purposes. Originally, a tribune represented a tribe of rulers then later it became known as a variety of officers. The tribunes were at first one, but their number was increased ultimately to ten. The two most important were the tribunes of plebs and the military tribunes. A Roman Tribune was a very high position. In certain ranks you had certain jobs, for example if my ranking was Tribune my job was to assist the legion commander, the Primus Pilus. If my ranking was Tribunus Cohortis I was the commander of a Cohort military unit. Being a Roman Tribune gave you the right to veto laws, command portions of the army, and eventually callShow MoreRelatedSpanish Dbq Essay649 Words   |  3 Pagesonly focusing on gold, glory, and God, but by strength and power as well. The age of exploration to the new world was dominated by the Spanish conquistadors. Their success in new discoveries brought great power and strength to Spain. In most circumstances, a country would do anything to become successful in the economy and government. 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Thursday, December 12, 2019

Commercial and Corporation Law Trading Parties

Question: Discuss about theCommercial and Corporation Lawfor Trading Parties. Answer: Introduction Commercial law refers to set of laws which stipulate the rights and guide relations and conduct of people and businesses engaged in trade and other business operations that are engaged in profit generating activities. Commercial law determines the rights and responsibilities of the trading parties, governs resolution of disputes arising from trade among other factors arising from business operations (Fu, 2007). On the other hand corporate law is the study of the relationship and interaction of various parties involved in business including customers, stakeholders, shareholders, the environment, company directors, and creditors among others ( Keay, 2011). It is basically the law that governs operations. PART A An entrenchment provision is a clause that allows or prohibits certain amendments of basic laws or the constitution for the purposes of protecting the rights of parties especially the minority. In business this is particularly important to maintain good relationship between the trading parties. David may want to have such provisions included in the companys constitution for a number of reasons. Any company operating in an area must be socially responsible to both its internal and external environments. This means that its operations must be in line with the expectations of both the external and internal environments as stipulated in the companys constitution or other laws guiding business operations. David could therefore be aiming at ensuring that business operations are mindful of both their internal and external environments. In business there are always the majority and minority groups. Whenever there are such associations there is always the tendency of the majority group to dominate over the minority of group hence infringing on their rights. In Organizations, the minority might be either employees or the public because in most cases they have to live by the decisions that are made by the management. Entrenchment provisions are therefore important to prevent the management from making dictatorial decisions that can negatively affect the minority groups. David could have therefore wanted the provisions to be put in place to ensure that these groups enjoyed their full rights. The provision also promotes stability. Whenever there are unregulated business operations disputes are likely to occur. In situation where the minority groups feel oppressed through unethical business operations such as unfair wages, unfair prices for goods and services among others they are likely to result into protests and pickets which hinders normal business operations. Such protests are likely to cause instability. David could have been aiming reducing such protest which in effect would lead to stability in business operations. PART B In any business operations each person has their duties and responsibilities clearly stipulated in their job description. Basically the job description is what guides the operations of each employee (Fazio, 2007). Basically a receptionist is mostly authorized to welcome visitors, answering phone calls, appointment calendars, receiving and sorting deliveries and performing of clerical duties among others. For any purchase to be termed as legal it must be budgeted for and approved by the financial officer. Any other route followed in making orders for purchases is not allowed. The receptionist has no authority for making any orders for goods and services on behalf of the company. This is basically the role of the purchase management department. By ordering for such goods the receptionist will be indulging in responsibilities that are not within his or mandate. In my opinion I think that the company is not legally bound to pay for the goods. This opinion is based on a number of factors .First of all, all purchase orders within an organization must meet the stipulated criteria for requesting for goods and services. Basically all purchases within an organization are made by the purchases department or in other departments the role is given to the procurement department .This means that all purchase requests must be forwarded to these departments for approval and implementation. All departments are required to establish all goods and services that are needed within department and prepare a budget for the goods then fill a purchase request form which is then forwarded to the procurement and finance departments for approval. The purchases department establishes the necessity of the goods or a service requested and later approves or rejects the request based on the necessity. If the request is approved, it is then forwarded to the finance department so that the budget can be approved and for payment to be authorized. The finance department can decline or accept the request depending on their ability to pay for the goods and services. This is the approved procedure for requesting for goods and services In Michelles case however, this procedure was not followed, so the company was not bound to pay office works. References: Keay, a. (2011). The corporate objective. Cheltenham, edward elgar pub. Http://public.eblib.com/choice/publicfullrecord.aspx?p=714169. Hanrahan, p. F., ramsay, i. M., stapledon, g. P. (2016). Commercial applications of company law. Fu, j. (2007). Commercial and corporations law. Geelong, vic, deakin university. Fazio, s. (2007). The harmonization of international commercial law. Alphen aan den rijn, the netherlands, kluwer law international. Tomasic, r., bottomley, s., mcqueen, r. (2002). Corporations law in australia. Sydney, federation press. Ma?ntysaari, p. (2012). Organising the firm: theories of commercial law, corporate governance and corporate law. Dordrecht, springer. Http://public.eblib.com/choice/publicfullrecord.aspx?p=885119.