Mixed-Ligands Complexes of L-Amino Acid and Ascorbic Acid

Mixed-Ligands Complexes of L-Amino Acid and Ascorbic Acid Electrochemical Studies of Mixed-Ligands Complexes of L-Amino acid and Ascorbic acid by Voltammetric Technique Meena* and O.D. Gupta ABSTRACT Studies of Pb(II) with amino acid L-Serine and Ascorbic acid have been carried out polarographically at pH =7.30 ±0.01,  µ=1.0M KNO3 at 25 °C.Pb(II) formed 1:1:1, 1:1:2 and 1:2:1 complexes with L-Serine and used as primary ligands and L- Ascorbic acid used as secondary ligand.. The values of stability constants (log varied from 2.25 to 11.45 confirm amino acids in combination with L-Ascorbic acid, their complexes could be used against Pb(II) toxicity. The stability constants of mixed ligand complexes have been evaluated by the method of Schaap and McMasters. For the comparison of the simple and mixed-ligands complexes, the mixing constants (Km) and stabilization constants (Ks) have been measured. The positive values of the mixing constants and stabilization constants show that the ternary complexes are more stable than the binary complexes. Keyword: Polarography, Stability Constant, Amino acids, Ascorbic acid, Voltammetric Technique. INTRODUCTION The L-amino acids and their compounds are used in biology, pharmacy, industry and laboratory reagent1-3. They control transamination, decarboxylation and metabolism process in human body. Mixed-ligands complexes of copper glycine with picolinic acid, quinaldinic acid, picolinic acid N-oxide, quinaldinic acid-N-oxide and with o-nitrophenol, 2,4-dinitrophenol have been carried out by D Prakash and coworkers [4-5]. The study of ternary complexes of different metal ions with amino acids and bicarboxylic acids have been carried out by Chandel et al.[6-9] On the other hand Vitamin C (L-ascorbic acid) is found naturally in a wide variety of plants and animals but not produced in human body and its only source is from diet10, L-Ascorbic acid is important drug used against cancer, scurvy and the risk of bronchitis or wheezing11-13. This drug helps the patient to strengthen the immune system. The person who suffered from AIDS has low concentration of Vitamin-C which is responsible for the form ation of various body components and organs but also keeps in order the immune system14-15. Its deficiency causes anemia, dental cavities and thyroid insufficiency. It forms chelate complexes with transition metal ions16 to produce a five membered ring with the enediol part of the molecule17. Pb(II) content is fixed in human body but whenever the concentration of Pb(II) increases, the human being suffers from severe diseases like cancer of the bladder, breast, intestine, leukemia system and sometimes death can also occur. Ascorbic acid is antioxidant alone and in combination with L-amino acids was found to be effective by increasing urinary elimination of lead. This beneficial role of Ascorbic acid was attributed to form complexes with lead18. Data suggest that some antioxidant can function as chelators and this dual benefit makes them strong candidates for treating lead poisioning19. The present study is related with the formation of binary and ternary complexes of Pb(II) with selected L-amino acids and Ascorbic acid by polarographic technique with the view that these drugs or metal complexes could be used against several severe diseases like cancer, AIDS and also metal toxicity. EXPERIMENTAL All polarograms were recorded on ELICO CL 375 DC Polarograph using a saturated calomel electrode (SCE) as the reference electrode and a platinum (Pt) electrode as counter electrode. The capillary had the following characteristics m=1.96 mg/s, t = 4.10 sec/drop and h = 40 cm. The reagents Vitamin C and amino acids were of AR grade and were used as complexing agents. KCl was used as supporting electrolyte to maintain the ionic strength at 1M. Triton X-100 of 0.001% in the final solution has been used as maximum suppressor. The temperature was maintained constant at 303 K. A glass cell is used as electrolytic cell in which all the three electrodes are immersed in test solution. N2 is used to remove the dissolved oxygen. Then increasing voltage was applied to record the current and with the help of the plot between current-voltage (polarogram) the value of E1/2 is calculated. RESULTS AND DISCUSSION Simple complex systems Before the studies of mixed-ligand, complexes, the formation constants of the complexes of lead with Vitamin C and lead with amino acid L-Serine and were determined by the method of DeFord and Hume25. The results are in good agreement with the literature. The values of formation constants of simple systems are presented in Table 1. The conditions corresponded as closely as possible to those for the mixed system. The half-wave potential of Pb(II) for each series ranged between -0.389 and -0.391 volt v/s SCE. Table 1: Stability constants for simple system Systems log à ¯Ã‚ Ã‚ ¢1 log à ¯Ã‚ Ã‚ ¢2 log à ¯Ã‚ Ã‚ ¢3 Pb(II)-VitaminC 2.25 3.18 Pb(II)-L-Serine 4.59 7.88 10.99 Mixed-Ligands Complex System In all the systems, solution containing 2.5 x 10-3 M Pb(II), 1M KC1 and 0.001% Triton X-100 was used. The concentration of weaker ligand (Vitamin C) was kept constant (0.001M and 0.01M) while varying the concentration of strong ligand (amino acids) in each case. In each case, a single well-defined wave was obtained. The plots of Ede v/s log id-i were linear with a slope of 30 ±2mV, showing that the two electrons reduction was reversible. The direct proportionality of the diffusion current to the mercury column indicated that the reduction was entirely diffusion controlled. A shift in half-wave potential to more negative side with the increase in amino acid concentration was observed. This shift in half-wave potential is greater in the presence of the weaker ligand than its absence. It signified mixed-ligands complex formation. The extended Shaap and McMasters26 treatment was applied and Ledens27 graphical extrapolation method to calculate the values of A, B, C and D. Data of calculation are given in table 2. Table 2: Values of A, B, C and D for Pb(11)-Ascorbic acid- Amino acids systems (Ascorbic acid concentration = 0.01M(fixed) System A B C D Pb(II)-Vitamin C-L-Serine 1.32 5.11 9.56 11.22 Table 3: Values of A, B, C and D for Pb(II)-Ascorbic acid Amino acids systems (Ascorbic acid concentration = 0.001M(fixed) System A B C D Pb(II)-Vitamin C-L-Serine 1.30 4.61 9.56 11.22 The stability constants à ¯Ã‚ Ã‚ ¢11 and à ¯Ã‚ Ã‚ ¢12 were evaluated from the two values of B. From the values of C two values of à ¯Ã‚ Ã‚ ¢21 were obtained which are in good agreement with each other. à ¯Ã‚ Ã‚ ¢30 is almost equal to D. The results are recorded in table 4 and the results are summarized in the form of schemes 1 and 2 where the numerical values indicate the log of the equilibrium constants. Table 4: Formation Constants of Mixed-Ligands Systems Systems log ÃŽ ²11 log ÃŽ ²12 log ÃŽ ²21 Pb(II)-Vitamin C-L-Serine 6.23 8.88 11.56 It has been observed that as the size of amino acids increased the stability of its complexes decreased20. The stability of L-amino acids complex also depends upon the chelate ring formation and basicities of ligands21. In case of L-serine and L-threonine, the stability of the latter is less than the L-serine complex owing to the fact that electron withdrawing OH group is nearer to L-threoninate complex than L-serinate complex, causing greater repulsive forces between metal and Off group in L ­-threonine complexes than L-serine complexes22. The same is evident from Pka values of L-amino acids23. In case of Vitamin-C, oxygen of enediol group may take part in bond formation with Pb(II), formed a five membered ring24. It is clear from the values of stability constant of the complexes that Vitamin-C and L-amino acids alone or in combination could be used to reduce the toxicity of Pb(II) in-vivo. One also has to consider the quantity of drugs that should not complex to the other essenti al metals present in-vivo and the same could be excreted easily from the body. On the other hand, the person who suffers from AIDS has low concentration of Vitamin-C, therefore his resistance can be increased by ascorbic acid therapy. The mixed ligands complex formation may also be explained with the help of schemes 1. The tendency to add X (X= amino acids) to PbX and PbY (Y=Vitamin C) can be compared. The logarithm values of stability constants of the above complexes are 3.29 and 3.98 for Pb ­-VitaminC-L-Serine. The tendency to add Y to PbX and PbY can also be compared. The log K values are (1.64, 0.93) and (1.47, 0.93) for Pb(II)-Vitamin C-L-Serine. This indicates that the addition of Vitamin C is preferred to Pb(amino acids) as compared to Pb(Vitamin C). The log K values for the addition of X to Pb[XY] and Pb[Y]2 are (5.33, 5.70) and (5.47, 5.58). This indicates that the mixed ligand complexation is favoured. The log K values for the addition of Y to Pb[XY] and Pb[X]2 are (2.65, 3.68) and (2.78, 3.65) for Pb(II)-Vitamin C-L-Serine and. This indicates that addition of VitaminC is preferred to Pb[X]2 over Pb[XY]. For comparing the stabilities of simple and mixed ligand complexes, it is convenient to measure the mixing constants. Km = and the stabilization constants. log Ks = log Km log2 The log Km values are 0.7 and o.49 and log Ks values are 0.398 and 0.188 for Pb(II)-Vitamin C-L-Serine and Pb(II)-Vitamin C-L-Threonine systems respectively. The positive values of mixing and stabilization constants show that the ternary complexes are more stable than the binary complexes. The tendency to form mixed-lingds complexes in solution could be expressed quantitatively in other approach compares the difference in stability (à ¯Ã‚ Ã¢â‚¬Å¾ log K), which is the result from the substraction of two constants and must therefore, be a constant. This corresponds to: à ¯Ã‚ Ã¢â‚¬Å¾ log K = Since more coordination positions are available for the bonding of the ligand [A] to a given multivalent metal ion,than for the second ligand [B]. > Usually holds i.e. one expects to observe negative values for à ¯Ã‚ Ã¢â‚¬Å¾ log K. Another more satisfactory, manner is to determine statistical values for à ¯Ã‚ Ã¢â‚¬Å¾ log K. The statistical values for regular octahedron (oh) is 5/12 and à ¯Ã‚ Ã¢â‚¬Å¾log Koh = -0.4. for a squar planer(sp), the value of à ¯Ã‚ Ã¢â‚¬Å¾ log K = -0.6 and for the distorted octahedron (oh), the statistical values i.e. à ¯Ã‚ Ã¢â‚¬Å¾ log K = lie between -0.9 to -0.3. The à ¯Ã‚ Ã¢â‚¬Å¾ log K values can be obtained using the following equations: à ¯Ã‚ Ã¢â‚¬Å¾ log K11=log à ¯Ã‚ Ã‚ ¢11-( log à ¯Ã‚ Ã‚ ¢10 +log à ¯Ã‚ Ã‚ ¢01 ) à ¯Ã‚ Ã¢â‚¬Å¾ log K12=log à ¯Ã‚ Ã‚ ¢12-( log à ¯Ã‚ Ã‚ ¢10 +log à ¯Ã‚ Ã‚ ¢02 ) à ¯Ã‚ Ã¢â‚¬Å¾ log K21=log à ¯Ã‚ Ã‚ ¢21-(log à ¯Ã‚ Ã‚ ¢20 +log à ¯Ã‚ Ã‚ ¢01 ) The observed values of à ¯Ã‚ Ã¢â‚¬Å¾ log K11, à ¯Ã‚ Ã¢â‚¬Å¾ log K12 and à ¯Ã‚ Ã¢â‚¬Å¾ log K21 are -0.61, 1.11 and 1.430 for Pb(II)-Vitamin C-L-Serine. The à ¯Ã‚ Ã¢â‚¬Å¾ log K values are higher than statistical values, which again prove that the ternary complexes are more stable than expected from statistical reason. ACTNOWLEDGEMENT The authors are thankful to the Head, Department of Chemistry, University of Rajasthan, Jaipur for providing facilities to carry out this research. REFERENCES + Chemistry Department, SKIT, Jagatpura, Jaipur, India-302025 Brosnan J, Nutr. J (2000) 130: 988S. Pisarewicz K, Mora D, Pflueger F, Fields G, Mari F, (2005) J. Am. Chem. Soc. 127: 6207. Wu G, Fang Y, Yang S, Lupton J, Turner N (2004) Nutr. J 134: 489. Prakash D, Shafyat M, Jamal A, Gupta AK (2005) Oriental J Chem 21:2. Prakash D, Safayat M, Jamal A, Gupta A K (2005) Oriental J Chem 21:3. Malhotra V, Chandel C P S, (2006) J Ultra Scientist Phy-Sci 18(2): 203-214. Jangid R K, Chandel C P S (2006) Ultra Chemist 2(2): 113-126. Verma M K, Chandel C P S, (2005) Oriental J Chem 21(1): 9-20. Malhotra V and Chandel C P S, (2006) Bull Electrochem 22: 301. Davies M B, Partridge D A and Austine J , Vitamin C: Its Chemistry and Biochemistry, Royal Society of Chemistry, London. (1991) Levine M, Rumsey S C, Wang Y, Park J B, Daruala R (2000) Biochemical and Physiological Aspects of Human Nutrition, Philadelphia, W B Saunders, p.541. Roomi M W, Ivanov V, Kalinovsky T, Niedzwiecki A, Rath M (2004) J Res Commun Mol Pathol Pharmacol 115. Martha H, Stipanuk W B (2000) Biochemical and physiological Aspects of Human Nutrition, Sounders Company. Fukuda S, (2005) J Curr Med Chem 12:2765. Harakeh S, Jariwalla R (1997)AIDS Res. Hum. Retroviruses 13:237. Davies M B (1992) Polyhedron 11:285-321. Hughes D L (1973) J Chem Soc Dalton Trans 2711. Dhawan M, Kachru D N, Tondon S K, (1998) Arch Toxicol 62: 301-304. Gurer H, Ercal N (2000) Free radical Biol Med 29: 927-945. Kapoor R C, Agarawal B S Principles of polarography (1991) Wiley Eastern Ltd New Delhi 71. Dodke R, Khan F (1993) J Indian Chem Soc 70: 15. Vajhallya S, Khan F (1999) J Indian Chem Soc 76:294. Mrudula Rao B V, Swamy S J, Lingaish P (1985) Indian J Chem 24 : 887. Allen R N, Shukla M K, Leszczynski J (2006) Int J Quant Chem 106:2366. DeFord D, Hume D N (1951) J Am Chem Soc 73:5812. Schaap W B, Mc Master D L (1961) J Am Chem Soc 83: 4699. Lenden I (1941) J Phys Chem 188:160.

Project Management Summary Essay

Strategic portfolio management plays an intricate part in project management. Through this paper, the reader will gain a stronger understanding of the relationship that strategic portfolio management plays in project management. Strategic Management Relation to Project Management Project management involves several parts, but the meaning must be understood first. â€Å"Project management is the planning, organizing, directing, and controlling of company resources for a relatively short-term objective that has been established to complete specific goals and objectives† (Kezner, 2013, p4). Knowing this allows the project manager to implement steps toward achievement of the defined goals and objectives. Part of these steps has to do with strategic management. Project management is strategically managed to advance the corporation’s organizational goals. Strategic management insures the right initiatives are pursued and supported with resources. Strategy today needs to align to a more fluid nature of business environments. It has to be flexible enough to adapt constantly to changing external and internal conditions. The relationship between strategic portfolio management and project management is a very important relationship. Strategic management compliments project management in that it attempts to ensure success by way of doing things at the most opportune time. If a company attempts something too early or too late then possible negative consequences may occur. Projects, within programs or portfolios, are a means of achieving organizational goals and objectives, often in the context of a strategic plan. Although a group of projects within a program can have discrete benefits, they can also contribute to the benefits of the program, to the objectives of the portfolio, and to the strategic plan of the organization. Conclusion As stated at the beginning of this paper â€Å"strategic portfolio management  plays an intricate part in project management†. The reader should now have a stronger understanding of the relationship that strategic portfolio management plays in project management. References Kerzner, Ph.D., H. (2013). Project Management: A Systems Approach to Planning, Scheduling, and Controlling (11th ed.). Retrieved from The University of Phoenix eBook Collection. Project Management Institute. (2013). A guide to the project management body of knowledge. (PMBOK guide). Newtown Square, Pa: Project Management Institute.

Jack Davis ( No Sugar Essay)

NO SUGAR (JACK DAVIS) Jack Davis’ â€Å"No Sugar†, written in 1985, is a play that highlights Australian racism and cultural destruction caused by British colonialism. It is set in 1929 (Great Depression) in Northam, Western Australia. The play explores the impacts of the European social and political philosophy of the early 20th century on Aboriginal society. The focal points of this play are the superiority of white people, racism, and the bond between Aboriginal families. These themes highlight Australian culture, and have shaped it into its many different forms for all Australian’s today.Jack Davis has used dialogue between the characters in this extract to privilege a postcolonial reading of the text. Davis uses dialogue in order to construct a world in which the aboriginal people can be identified to the audience as an ill-treated, oppressed race. Davis uses dialogue to represent how the colonized react to the social situations in which they were subjugated to, on a regular basis in the early times of colonization. â€Å"CISSIE: Aw mum, Old Tony the ding always sells us little shriveled ones and them wetjala kids big fat one. Through this dialogue the audience identifies that society at the time did not allow the colonized to be classed as the same standard as the colonizer. Davis lends this text to a postcolonial reading through the use of characterization. The use of characterization in the play reinforces the idea that the characters amplify a sort of submission to English culture displays to the audience the effect of colonization. Although the characters retain many of their aboriginal attributes, such as living off the land â€Å"Come on, let’s get these rabbits. They have allowed themselves and their culture to be colonized by accepting many of the British attributes such as playing cricket â€Å"DAVID and CISSIE play cricket with a home-made bat and ball. † The aboriginal people have allowed themselves to colon ized acquiring British aspects, which coincide with their aboriginal heritage. Through this extract the characters also begin to read the paper, the combination of the children playing cricket and the elder reading the paper appears from an outside point perspective a very British activity. Looking at the context, which surrounds the writing of the play, can also support a postcolonial reading.Another device used by Davis is stage directions principally used to invoke or create a rising dramatic tension, an example of this is â€Å"He nicks his finger with the axe and watches the blood drip to the ground. † This is symbolic of the Aboriginals manifesting frustration; they are inflicting pain on themselves because they know it isn’t possible to inflict pain on their conquerors. Jimmy’s character represents the rebellion of any marginalized race; he pushes the boundaries as far as he can. The fact that Aboriginals are â€Å"dancing† for the white Australian s shows their power.This dancing is a form of service provided by the Aboriginals, they are expressing their culture but to the people who have destroyed it. It could almost be read as a child trying to get an adults attention by jumping around and holding out what they want. To Jimmy these dancing Aboriginals are jumping around and showing the White Australians that they want their culture back. This reach out to white settlers shows how much more dominate they are and their culture is. Through the use of dramatic conventions Jack Davis’ play No Sugar can be read as a postcolonial criticism.It presents a number of issues with colonization and the particular effects it had on the Australian Aboriginal people. First performed in 1985, the play deals with the struggles of the aboriginal people and oppression in which they endured by white Australian society. The play was set in 1929, a time when aboriginal people were not yet accepted as equals in society. The main ideas presen ted in the play are shown through the dialogue, characters and context. This extract uses techniques to set the basis for the idea’s that will be expressed throughout the entire play.

Self-Esteem Essay - Obedience - Free Essay Example

Sample details Pages: 3 Words: 786 Downloads: 4 Date added: 2017/09/16 Category People Essay Type Argumentative essay Tags: Teenager Essay Did you like this example? Alexandra L. Locsin A56 Aug 18/10 Writing Task: Self-Esteem Essay Obedience [pic] Obedience A person is defined according to his or her own manners, good moral values and right conduct. All of these say so much about a person’s personality. It is because of her personality she could be treated fairly and looked up to because of how she treats other people. Ones personality could bring her to the top and conquer all that gets in the way. One important value a person could possess is obedience. Obedience is when you learn to follow rules and treat these rules as a treasure for success. There are so many rules that each and every one of us should follow. One of these rules comes from our own parents. Our parents nurtured us from day one. All their sweat and hard work are for us, their children. For this, we too should treat them right and by simply obeying to their rules as our parents; it makes them feel secured that nothing wrong would ever happen to us. Their rules are probably even the most important and simplest of them all. Some of them may be letting them know where we are and who we are with or coming home on or before the time they told us to come home and even helping our siblings with the household chores. Also, respecting them and putting ourselves in the right position is a simple sign of obedience. As for Filipinos like us, learning how to address the elders with â€Å"po† or â€Å"opo† is already a sign of obedience. When we learn to follow these and not whine about what the elders are telling us, we could say that we are obedient daughters or sons. As teenagers, it is our obligation and right to come to school. In our schools, we also have so much rules to follow, may it be in our classrooms or in the whole campus. When our professor tells us to search for some sources for our paper or bring certain materials for our project and we do it, it is a sign of obedience. When our classmate asks for our favor to do a certain part of our group project and we do it, it also is a sign of obedience. These are just the simplest form of obedience in school. Sometimes, we may even have to follow even bigger and more complex rules such as those that our student handbook states. Following the dress code, respecting our professor in and out of the classroom, not cutting classes, staying away from off-limit places and not bullying our schoolmates are some of those campus rules that we have to follow. When we do, we are obviously obedient students and we should be proud of this. We all belong to a certain community and it is important that we work as one to create a difference in our society. If I, for one, follow all rules and regulations that our community dictates, then in my simplest way I am helping in creating or starting a change. This helps a lot because if other people see that the change I have started is slowly making a difference then they too may start a change themselves. Through this w e all are working as individuals and together as one to create the biggest change of all. This is a sign that people in our community are obedient. It is because of our obedience that the world is progressing and is gradually changing to its best. We all should be obedient to anyone in our surroundings; obedient to our parents, to our professors, to the leaders in our society and basically, to anyone. It is also important that we know when we should be obedient. If you are asked to do something wrong or improper then obviously it is alright to forget about being obedient. Yet if we are asked to do something right, then put yourself in a much better place and simply do what’s asked of you. This is not hard to do especially when it gives other people a good impression of you. So basically, when I am trying to say is that being obedient is really important and we should never forget about it. We always should know why we should be obedient, to whom should we be obedient an d when should we be obedient. Let’s just say that possessing this value says a lot about who we are and it is important for other people to see it so that we would have a good impression on anyone and that people may want to be friends with us and influenced by us. Se Don’t waste time! Our writers will create an original "Self-Esteem Essay Obedience" essay for you Create order