Chemical Reactions of Amino Acids:
You may ask: what is the relevance of chemical reactions in the study of biological phenomena? Let us consider few of such reasons. First, taking advantage of chemical reactivity of certain amino acids has permitted chemical modification of proteins. Secondly, qualitative detection and quantitative measurement of amino acids and proteins were possible because scientists have taken advantage of coloured solution formed when these acids are made to react with certain chemical reagents. Another very important reason is that the biological function of proteins is known to be closely linked with the chemical behavior of their R groups.
Reactions of α-Carboxyl Group:
The α-carboxyl group can react with ammonia and primary amines to yield unsubstituted and substituted amides respectively.
i)
ii)
iii)
Reactions of α-amino Group:
i) Free α- amino groups of amino acids may react with aldehydes to form Schiff bases.
ii) Acylation: amino groups can be acylated with acid anhydrides and acid halides.
iii) Ninhydrin Reaction
Amino acids, through amino groups can react with ninhydrin (or triketohydrindene hydrate), the very strong oxidizing agent. This agent oxidatively deaminate α- amino functional group of amino acids. Products of the reaction are carbon dioxide, aldehyde, ammonia, and hydrindantin.
The significance of the reaction is in its application in spectrophotometric quantification of amino acids at 570 nm. [α-imino acids, example Proline and Hydroxyproline, yield yellow complex instead of purple, with absorption maxima at 440nm].
Reactions of Specific Functional Groups of Side Chain:
Specific reaction of amino acids is significant for sequencing, degradation and chemical synthesis of peptides and proteins. These reactions are helpful in recognizing specific functional groups and therefore specific amino acids having such functional groups.
i) Reactions of Sulfyhydryl Group:
a) Disulfide bond (bridge) formation
Thiol groups of cysteine can react with one another to create disulfide species.
b) Reactions of cysteine with iodoacetic acid.
Cysteine is also known to react with iodoacetic acid to yield S-carboxymethyl cysteine derivatives.
ii) Xanthoproteic Reactions of Aromatic Ring:
Amino acids with aromatic nuclei create yellow nitro derivatives on heating with concentrated nitric acid. This reaction is based on nitration of benzene ring with concentrated HNO3 yielding yellow derivatives of nitrobenzenes. Reaction is provided by tyrosine, tryptophan, and polypeptide that have these amino acids. Phenylalanine is more difficult to nitrate and so needs H2SO4 as a catalyst.
iii) Millon's Reaction:
Amino acid called tyrosine, a hydroxybenzene-radical containing compound, reacts with Millon's reagent (a solution of mercuric and mercurous ions in nitric and nitrous acids) to form red complexes.
iv) Reaction of Tryptophan with Formaldehyde:
Tryptophan reacts with formaldehyde reagent in presence of concentrated H2SO4, to create a bluish- purple compound appearing as ring at interface of liquids. This reaction is characteristic of indole- ring of tryptophan.
v) Sakaguchi Reaction:
Arginine, an amino acid containing guanidinium group, reacts with α- naphthol and oxidizing agent, like bromine water, to provide a red color compound.
Tutorsglobe: A way to secure high grade in your curriculum (Online Tutoring)
Expand your confidence, grow study skills and improve your grades.
Since 2009, Tutorsglobe has proactively helped millions of students to get better grades in school, college or university and score well in competitive tests with live, one-on-one online tutoring.
Using an advanced developed tutoring system providing little or no wait time, the students are connected on-demand with a tutor at www.tutorsglobe.com. Students work one-on-one, in real-time with a tutor, communicating and studying using a virtual whiteboard technology. Scientific and mathematical notation, symbols, geometric figures, graphing and freehand drawing can be rendered quickly and easily in the advanced whiteboard.
Free to know our price and packages for online biology tutoring. Chat with us or submit request at [email protected]
tutorsglobe.com self pollination assignment help-homework help by online sexual reproduction tutors
in the second generation of computers that the concept of programming language, Central Processing Unit (CPU), memory, and input and output units were developed.
over the past 25 years, the environment in which businesses operate has become more and more competitive and turbulent.
tutorsglobe.com aggregate demand assignment help-homework help by online demand tutors
Magnetism as a Relativistic Phenomenon tutorial all along with the key concepts of Electric Charges As Seen By Different Observers In Different Frames of Reference, Electric and Magnetic Forces
Classification of algae tutorial all along with the key concepts of PROKARYOTIC ALGAE, EUKARYOTIC ALGAE, Division Cyanophyta, Division Chlorophyta, Division Phaeophyta, Division Rhodophyta, Division Xanthophyta, Division Euglenophyta, Division Dinophyta, Division Bacillariophyta
The process that generates recombinations of gene through interchanging of corresponding segments among the nonsister chromatids of homologous chromosomes, is known as recombination of chromosomes.
Theory and lecture notes of Sequences and Probability all along with the key concepts of Experiment, Outcomes, Sample Space, Event, Arithmetic Sequences, Binomial Theorem. Tutorsglobe offers homework help, assignment help and tutor’s assistance on Sequences and Probability.
tutorsglobe.com pasteur vaccine for rabies assignment help-homework help by online microbes in fermentation tutors
Theory and lecture notes of Chi-square goodness-of-fit tests all along with the key concepts of chi-square goodness-of-fit tests, homework help, assignment help. Tutorsglobe offers homework help, assignment help and tutor’s assistance on Chi-square goodness-of-fit tests.
www.tutorsglobe.com offers functional group reactions in organic chemistry homework help, functional group reactions assignment help, online tutoring assistance, organic chemistry solutions by online qualified tutors help.
theory and lecture notes of construction and mechanism of operation all along with the key concepts of construction of bjt, operation of n-p-n bjt, current components, minority carrier profile and notation to an n-p-n bjt. tutorsglobe offers homework help, assignment help and tutor’s assistance on construction and mechanism of operation.
tutorsglobe.com scanning electron microscope assignment help-homework help by online electron microscope tutors
Carboxylic Acids and their Derivatives tutorial all along with the key concepts of General Formula of Carboxylic Acids, Derivatives of Carboxylic Acids, Naming Carboxylic Acids, Structure of Carboxylic Acids and Physical Properties of Carboxylic Acids
tutorsglobe.com concept of working capital assignment help-homework help by online working capital management tutors
1947168
Questions Asked
3689
Tutors
1450626
Questions Answered
Start Excelling in your courses, Ask an Expert and get answers for your homework and assignments!!