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Authors: Singh, Harbhajan
Issue Date: 1969
Abstract: The name protein was first of all introduced by Mulder (Din 1839 who derived it from the Greek Word proteios(meaning first). Proteins are naturally occuring (in the protoplasm of all animal and plant cells) macromolecules having one or more than on© polypeptide linkage in them. In addition to carbon, hydrogen, oxygen, nitrogen and sulphur, they also contain elements like phosphorous* Proteins are optically active colloids having no characteristic melting points and may be coagulated by heat, inorganic acids and bases. They are amphoteric in nature and their behaviour as an anion or a cation depends upon the pH of the solution,eharact#rlstie of each protein. When the solution contains equal number of anions and cations the protein is said to be at the isoelectric point. At this pH the protein has its least solabllityfosmotic pressure, viscosity etc.* On the basis of their physical and cheiaical characteristics proteins may be classified into simple and conjugated proteins. The former give •c-aoino acids on hydrolysis while the later contain a non-protein part(known as the prosthetic group) which can be separated from the protein by careful hydrolysis. Besides,there are derived proteins which represent degradation products obtained by the action of acids,alkalis or enzymes on proteins* Structurally proteins are macromolecules having poly-peptide linkages and are of two typettfibrous and globular* In the fibrous proteins,namely.wool halr.sllk etc.,the polypeptide choins are extended* In other cases, however,the chains are apparently 'coiled* and these may be extended by the application of force. The folded form of a fibrous protein is known as the *-form and the extended as the p-form. The globular (corpuscular) proteins, namely, insulin, albumin etc.,are ©ore compact than the fibrous proteins, but their shape is non-spherical (e.g.,x-ray studies have shown that haemoglobin has a cylindrical shcpe), Of the two it is only the globular which is obtained in the crystalline form* The fibrous protolns lack the characteristics necessary for the crystalline form due to the fact that all protein crystals grow from solution contain solvent, the removal of which causes the protein to become lest crystalline* The solvent has been shown to be Interstitial arid not 'solvent of crystallisation*. The proteins undergo modification in composition and structure on reacting with suitable reagents. Studies on such proteins can be of interest both from th© theoretical and applied view point. Theoretical interest is directed toward determining the nature of their structures which are responsible for the distinctive biological action of certain proteins like antigens,hormones, pepsin and tabacomosaic virus (2-10). The practical interest is,for the most part focussed,on the modification of the undesirable properties of certain proteins so that they may be used medicinally (e*g»preparation of toxoids and vaccines). The work on the conjugation of carcinogens to protains (11 -14) for the purpose of producing antlserabrldges is a typical case involving the modification of protein structure in removing the undesirable properties and malting them medicinally useful, The reaction of proteins with many synthetic deter^nts is of considerable interest. It appears that all detergents or substances having S0a0H group produce a tanrdng effect on proteins,which may be due to cross linking through the sulfonate or sulphate group, rather than the dennturation only,alt*sough the phenomena observed could be obtained on the basis of denaturatlon with unfolding of the protein molecule(15,16 ). In recent years considerable work has been done on the use of alkyl sulfonates in gastric ulcer therapy. The desired effect is the inactlvation of the pepsin.The mechanism may involve crosslinkages (17-23) which would entail mutual affinity of the hydrocarbon portions of detergent ions bound to adjacent protein molecules. Proteins,although basically different from the high polymers in their structure (with free terminal groups), have found some uses in plastics and in the manufacture of fibres. In both caset modified protein products are obtained through interaction with formaldehyde,a process involving trie Joining of the two protein chains by means of a methylene (-CH« ) group. Various patents from time to time have appeared in the literature for preparing casein fibres (24) casein wool and casein filaments (26)* In all these mixtures of casein with sodium lauryl sulphate and formaldehyde it extruded in a coagulating bath containing sodium alueinate and zinc chloride. Casein fibre has an opaque silk like lustre similar to natural protein fibres and resembles certain types of rayons. Here formaldehyde Is used to establish methylene bond but the extra tensile strength and elasticity is realized from aluminium sulfonate or sodium alumlnate by forming aluminium bridges. The recent development is the use of iodlnated proteins as a dietary supplement in animal husbandary. By the Judicious use of iodincted casein, it is possible to stimulate increased milk production in cows, improve libido and fertility in active bulls,induce s slight advantage in growth rate and economy of gain in young pigs and possibly improve egg production in chicken. The physiological effects of iodlnated proteins are largely due to their thyroxine content. CHARACTERISATION OF METAL-PROTEIN COMPLEXES, Many complexities arise during the investigations on proteins which are attributed to factors like,uncertainty in molecular weight,variation in chemical behaviour depending upon the nature of origin,purity and their sensitivity to denaturation. A large number of physico chemical methods, viz.,ultracentrlfugation (26,27) ultrafiltration (28-32), magnetic susceptibility (33-35 ) ,light scattering (36-38 ) , solubility (39) ,viscosity (40) precipitation (41-43 ) , migration in electrical field (44-46 ) ,polarography (47-56 ) , spectrophotometry (57-68 ) and electrophoretic mobility (69f52 ) have been used extensively in ascertaining the mode of binding of metals to proteins and in achieving greater success in quantitative aspect of the problem. The first important factor in the study of metalprotein interactions is the knowledge of the hydrogen ion equilibria studies of the proteins. These studies are indispensable for the determination and characterization of different ionisable sites of the protein,acting as donor groups for the coordinotion of metal ions.
Other Identifiers: Ph.D
Research Supervisor/ Guide: Malik, Wahid U.
metadata.dc.type: Doctoral Thesis
Appears in Collections:DOCTORAL THESES (chemistry)

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