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Globular Protein Stability

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A knowledge of the origin of the stability of proteins in aqueous solution is essential to the understanding of their structure and function. The stability of a globular protein in aqueous solution can be determined by studying the disruption of its native structure, i.e., the process of denaturation[1]. In this process the native folded protein structure is converted into a form that is predominantly unfolded but can still possess some residual folded structure[2]. Consequently, the fully unfolded or random-coil state of protein, which is the ideal reference state in discussions of the thermodynamic stability of proteins, is not always experimentally accessible[2]. Through model systems consisting of peptides or shortened proteins, it is …show more content…

This may be attributed to the fact that the addition of sugars to the protein increases the hydrophobic, electrostatic and hydrogen-bonding interactions giving rise to the compact form of protein. Therefore, by observing a decrease in the compressibility of the solution and the increase in the apparent molal volume of the protein after the addition of sugars, we can say that the extent of denaturation of protein is reduced and its stabilization has taken place Proteins are stabilized by a combination of hydrogen-bonding interactions, electrostatic interactions and hydrophobic interaction. In some proteins there is an additional contribution from cross-linking, metal complexing and specific binding of ions and cofactors. In discussing the effect of different sugars on the stability of hemoglobin, we have to consider the effects of different sugars on these various forces and interactions. In aqueous solutions of protein, there is a cooperative hydrogen–bonded structure.[6] When sugar is added to the protein solution, the OH groups of sugars may also compete for hydrogen-bonding.[6] Now we have to consider the respective interactions between protein, water and additive (sugar) molecules. The additive interacting more strongly with protein than with water will tend to stabilize the denatured states by the formation of protein additive complexes. They will, therefore, have a denaturing effect. However, additives interacting more stronglywith water molecules than with protein will favour the stabilization of protein

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The effect of pH on the speed of enzyme interaction with substrate chemicals Hypothesis: About pH: If the pH level is less than 5, then the speed of the enzyme reaction will be slower. About temperature: If the temperature stays the same, then the speed of the enzyme reaction will not be completely affected. Background information: The function of enzymes is to speed up the biochemical reaction by lowering the activation energy, they do this by colliding with the substrate.

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Sucrase activity increases with increasing sucrose concentration Materials and Methods Effect of pH on Enzyme Activity 1. Dependent Variable amount of product (glucose and fructose) produced 2. Independent Variable pH 3. Controlled Variables temperature, amount of substrate (sucrose) present, sucrase + sucrose incubation time Effect of Temperature on Enzyme Activity 1.

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55 degrees celcius Table 6: Effect of Sucrose Concentration on Sucrase Activity Optical Density 35 g/L 30 g/L 25 g/L 20 g/L 15 g/L 10 g/L 5 g/L 0 g/L 1 1.007 0.974 0.950 0.926 0.849 0.734 0.515 0.003 2 1.002 1.011 0.947 0.937 0.834 0.766 0.496 0.002 3 0.980 0.998 0.944 0.932 0.838 0.754 0.495 0.001 average 0.996 0.994 0.947 0.932 0.840 0.751 0.502 0.002 Effect of Sucrose Concentration on Sucrase Activity 5. State how sucrase activity changes with increasing sucrose concentration. First sucrase activity increases greatly. After 10 g/l sucrase activity continues to increase but at a slow rate until it reaches 30 g/l. At 30 g/l to 35 g/l sucrase activities mostly stayed the same

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However, all proteins are constructed from the same set of 20 amino acids linked in unbranched polymers. The covalent bond that exists between amino acids is called peptide bond, hence a polymer of amino acids is named polypeptide. A protein is a biological functional molecule made up of one or more polypeptides which is folded and coiled into unique three-dimensional structure. In laboratory, it is important to measure the concentration of proteins for research investigations. Biuret test is adopted to quantify proteins in fluid by using a spectrophotometer.

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The enzymeʼs have an active site that allows only certain substances to bind, they do this by having an enzyme and substrate that fit together perfectly. If the enzyme shape is changed then the binding

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Homework 4: Experiment Analysis 1. Do the solutions we are experimenting test positive for protein, starch, or sugar? 2. Chemical indicators are used to detect certain molecules. These are often used to test for supplements to recommend to consumers.

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The hypothesis stated that if sucrose was added to the yeast, then the greatest amount of CO2 would be produced because sucrose contains glucose as one of its individual sugar units, which is the primary food source for eukaryotic cells undergoing aerobic cellular respiration. This hypothesis was supported by data from the group and class averages. According to the group data, sucrose had the greatest respiration rate at 35.94 ppm/s, then agave at 20.22 ppm/s, honey at 13.69 ppm/s, and the lowest respiration rate water, at 3.63 ppm/s. The class data was as follows: sucrose with 13.66 ppm/s, Honey with 11.24 ppm/s, agave with 11.09 ppm/s, and finally water with the lowest respiration rate again at 3.03 ppm/s. The group’s data for sucrose was

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(Matthews R.H , 1987) In addition to naturally occurring sugars, many processed foods and beverages contain added sugars mainly in the form of sucrose and high fructose corn syrup. Refined carbohydrates are added to

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has a slight higher affinity for oxygen than haemoglobin, especially at lower layers. This is because myoglobin has an easier job in that it only needs to store oxygen and release it for the muscles, while haemoglobin also has to transport the oxygen and release it in the correct areas. Haemoglobin is formed in the body by DNA just like all the other proteins. Alterations or mutations to haemoglobin causes many blood related diseases such as sickle-cell anaemia. Where the cell structure is coloured and can no longer hold as much oxygen in the right way as a normal blood cell.

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Along with being found in plants, they are also present in liver cells, kidney cells, leukocytes and erythrocytes. For the concentration of enzyme experiment, the hypothesis was if the concentration of an enzyme increases, then the enzyme activity will increase as well. The hypothesis was proven to be true, because there are more enzymes to react with substrates. For the enzyme—factors affecting, the hypothesis concluded was if the temperature increases, than the enzyme activity will increase. This however was proven wrong, because enzymes become unstable at higher temperatures.

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1% glucose, 1% maltose and 1% lactose all progressively get positive results by changing colours to reddish brown at the end of this experiment. In this case the aldehyde functional group that is present in the products (monosaccharides and some disaccharides) in this reaction is able to reduce copper in the presence of alkali and this produces colour changes while converting to an aldose sugar. Honey is made of fructose and glucose which instantly turned brown after the test-tube was placed in the boiling water because of its active aldehyde and carbonyl group. The copper (II) sulphate present in the Benedict’s solution reacts with electrons from the aldehyde group which results in a redox reaction to from cuprous oxide, a red brown precipitate that seen in all of the above mentioned solutions (Hill, 1982). Beer also gave positive results because it contains aldehydes and ketones (i.e. acetone, trans-2-butenal, furfual) during its beer production process where the sugars are converted through fermentation (Hill, 1982).

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It was well known that the collisions between enzyme and substrate molecules increased with an increase in temperature that result in an increase in reaction rate and thus the conversion. It was observed that with an increase in enzyme loading from 1-2% (w/w) increase in percentage conversion. Usually, an increase in enzyme loading increases the number of active sites and therefore more substrate molecules converted into products. The highest conversion could be attained when the enzyme loading was taken to be 2% in combination with the temperature 50 ˚C.

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Summary In this lab our primary goal was to learn about the kidney and its filtration abilities as well as how the kidneys maintain blood composition by altering the urine composition. As well as to see the effects glucose, protein, salt, and water intake have on the urine composition and volume. To do this we will use multistix test strips to test the urine before the intake in fluids and then once again after the glucose, protein, salt, or water is consumed. The last objective is to understand the relationship between urine output and various conditions and diseases, this is done through the use of several multistix test strips and descriptions of several people's characteristics and their diseases.

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ADVANCED GLYCATION END PRODUCTS Advanced glycation end product as an oxidative process that occurred in food perserved or heated the presence of reducing sugars were first observed in early 1900s which non-enzymatically make the food proteins insoluble with yellowish fluorescent products attached to them. This process is known as Maillard reaction named on its discoverer the Louis C. Maillard in 1912 (Finot ., 2005). The Maillard reaction is the one of physiological significance. In vivo, it is also observed that human protein non-enzymatically glycated in the presence of physiologic sugars. One of the best characterized glycation product known to occur in the body is glysocylated hemoglobin.

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The enzymes are denatured because higher temperatures cause the enzyme

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