ALBUMIN, or ALBUMEN (

See also:

• LAT

Lat. albus,

See also:

• WHITE
• WHITE, ANDREW DICKSON (1832– )
• WHITE, GILBERT (1720–1793)
• WHITE, HENRY KIRKE (1785-1806)
• WHITE, HUGH LAWSON (1773-1840)
• WHITE, JOSEPH BLANCO (1775-1841)
• WHITE, RICHARD GRANT (1822-1885)
• WHITE, ROBERT (1645-1704)
• WHITE, SIR GEORGE STUART (1835– )
• WHITE, SIR THOMAS (1492-1567)
• WHITE, SIR WILLIAM ARTHUR (1824--1891)
• WHITE, SIR WILLIAM HENRY (1845– )
• WHITE, THOMAS (1628-1698)
• WHITE, THOMAS (c. 1550-1624)

white)  , an organic sub-stance typical of a group of bodies (albumins or albuminates) of very complicated chemical composition . They are sometimes called the histogenetic bodies or proteids, because they are essential to the building up of the animal organism . The vegetable kingdom is the original source of albuminous sub-stances, the albumins being found in greatest quantity in the seed . They also occur in the fluids of the living organism . The chemistry of the albumins is one of the most complicated and difficult in the whole domain of organic chemistry . It has attracted the attention of many workers, and has formed the subject of a huge literature . In this field Bechamp, Cohnheim, Albrecht Kossel, and, especially, Emil Fischer and his pupils have been extremely active . The general trend of these researches lies in the study of the decomposition or " breaking down " products of the albumin molecules; once these are accurately determined, the synthesis of an albumin is but a matter of time . Already we have proceeded far in our know-ledge of the decomposition products, and certain simple proteids have been synthesized . The albumins contain in all cases the elements carbon, hydrogen, nitrogen, sulphur and oxygen; their composition, however, varies within certain limits: C=50-55 %, H=6•9-7.3%,N=15-19%,S=0•3-2.4%,0=19-24%, crystallized albumin is C=51.48 %, H=6.76 %, N= 18.14%, S= o.96 %, 0= 22.66 %, which points to the formula C72oHnsuN2isS50sas, corresponding to the molecular weight 16,954 . A high molecular weight characterizes these substances, but so far no definite value has been determined by either physical or chemical means; A . P .

Sabanezhev obtained the value 15,000 by

Raoult's method for purified egg albumin . All albumins are laevo-rotatory; and on incineration a small amount of inorganic ash is invariably left . They are usually insoluble in water, alcohol and ether; and their presence as solutes in vegetable and animal fluids is not yet perfectly under-stood, but it is probably to be connected with the presence of salts or other substances . A remarkable change occurs when many albumins are boiled with water, or treated with certain acids, their solubility and general characters being entirely altered, and the fluid becoming coagulated . This change is seen II General char-asters . in the transformation of the " white " of an egg on boiling . Albumins are generally detected by taking advantage of this property, or of certain colour changes . The reagents in common use are: Millon's reagent, a solution of mercuric nitrate containing nitrous acid, this gives a violet-red coloration; nitric acid,. which gives a yellow colour, turning to gold when treated with ammonia (xanthoproteic reaction); fuming sulphuric acid, which gives violet solutions; and caustic potash and copper sulphate, which, on warming, gives a red to violet coloration (biuret reaction) . Boiling with dilute mineral acids, or baryta water, decomposes albumins into carbon dioxide, ammonia and fatty amino- and other acids . These decomposition products include: Decom" 1 cocoll or aminoacetic acid, NH2CH2COOH, position g y ' products. or aminopropionicacid,CH3•CH(NH2)•000H,a-amino- butyric acid, a-aminovalerianic acid, leucin or isobutyla-aminoacetic acid, (CH3)2CH•CH2•CH(NH2)•000H, isoleucin, probably 0-aminocaproic acid, serin or a-amino-f3-hydroxypropionic acid, HO•CH2•CH(NH2)•COOH, aspartic acid or aminosuccinic acid, HOOC.CH2.CH(NH2)•COOH, glutaminic acid or a-amino-n-glutaric acid,H000• (CH2)2• CH(NH2) • COON, diaminoacetic acid, a-13-diaminopropionic acid, lysin. or a-e-diamino-n-caproic acid, NH2(CH2)4 . CH (NH2) • COON, arginin or guanidine-a-amino-n-valerianic acid, (NH) (NH2) C•NH• (CH2)3•CH(NH2)•COOH, ornithin or ab-diamino valerianic acid, NH2.(CH2)3.CH(NH2)•000H, histidin or a-amino-/3-imidazol- I propionic acid, HOOC . CH(NH2) • CH2 .

C : CH .N :CH • NH, proline i I or a -pyrrolidin carboxylic acid, HOOC•CH•NH•CH2•CH2•CH2, hydroxyproline, phenyl alanine or phenyl-a-aminopropionic acid, C61-15 . CH2• CH (NH2) . COOH,tyrosine or p-hydroxyphenyl-aaminopropionic acid, . phenyl ethylamine, p-hydroxyphenyl ethylamine, tryptophane or indol aminopropionic acid, A. cystin (protein-cystin) or a-amino-$-thioglyceric acid " disulphide," (S . CH2• CH(NH2) • COOH) 2, B. cystin (

stone-cystin), or a-thio-fl-aminoglyceric acid " disulphide," (NH2•CH2•CH : S . COOH)2 . This list is not exhaustive; other products are given in Gustav Mann, Chemistry of the Proteids (1906), to which reference should be made for a complete account of this. class of compounds . The complexity of composition militates in a great measure against a rational classification of albumins by purely chemical considerations . Such classifications have been at- .assm- tempted by A . Kossel and by W . Kiihne and E . P . Pick; canon of albumins. but in the present state of our knowledge, however,- the older classification of E .

Dreschel and F . Hoppe-Seyler, based primarily on solubilities and

distribution, may be conveniently retained . This classification is with certain modifications as follows: I . Albumins proper: characterized by having colloidal solutions . Albumins: serum-albumin, egg-albumin, lactalbumin . Globulins: serum-globulin, egg-globulin, lactoglobulin, cell-globulins . Plant-globulins and plant-vitellines . Fibrinogen . Myosin . Phosphorus containing albumins (nucleo-albumins), caseins, vitellines, nucleo-albumins of the cell-protoplasm, mucoid nucleo-albumins . (7) Histones . (8) Protamines .

II . Transformation products of the albumins proper . (i) Acid-albumins,

alkali albuminates . (2) Albumoses, peptones and peptides . (3) Halogen-albumins, oxyprotein, oxyprotsulphonic acid, &c . (i) Nucleo-proteids . (2) Haemoglobin and allied substances . (3) Glyco-proteids, mucins, mucoids, helico-proteid.IV . Albuminoids . (r) Collagen . (2) Keratin . (3) Elastin .

(4) Fibroin . (5) Spongin, &c . (6) Amyloid . (7) Albumoid . (8) Colouring matters derived from albumin . Albumins proper.—Albumins (as classified above) are soluble in water, dilute acids and alkalies, and in saturated neutral

salt solutions; they are coagulated by heat . " Serum-albumin," or " blood-albumin," possibly C4i H7nNusSSOi4o, occurs in blood-serum, lymph, chyle, milk, &c.; its coagulation temperature is about 67° . It differs from egg-albumin in its specific rotation (–57° to -64°), and in being slowly coagulated by alcohol and ether . Egg-albumin is the chief constituent of the white of egg; this fluid also contains a globulin and a mucoid . It coagulates at about 56°, and its specific rotation is -30• 70° . " Lact-albumin " occurs in all kinds of milk . The globulins are insoluble in water and in dilute acids, but soluble in alkalies and in neutral salt solutions; these solutions are coagulated on boiling .

" Serum-globulin," also termed globulin or fibrino-plastic globulin, paraglobulin and paraglobin; occurs in blood serum; " cell-globulins " occur in many

organs diver, kidneys, pancreas and the thyroid gland, also in muscle-plasma; " crystalline," a globulin occurring in two forms a and 13, is found in the lens of the eye; " egg-globulin " and " lactoglobulin " occur respectively in the white of egg and in milk . , Plant albumins or phyto-albumins have been chiefly investigated in the case of those occurring in seeds; most are globulins, insoluble in pure water, but soluble in salt solutions; " Q edes'tin," a globulin of this class, is very widely distributed . Other varieties or classes of these compounds are: plant caseins; phyto-vitellines, legumins and conglutins . Fibrinogen occurs in the blood plasma, and is changed by a ferment into fibrin, to which the clotting of blood is due . Fibrinogen is insoluble in water, but soluble in salt solutions; it has three different coagulation temperatures, 56°, 67 75° . Fibrin, produced from fibrinogen by a:ferment, is a jelly-like substance; coagulable by heat, alcohol, &c . The muscle-albumins include " myosin " or paramyosinogen, a globulin, which by coagulation induces rigor mortis, and the closely related " myosinogen " or myogen; myoglobulin and myoalbumin are also found in muscles . The nucleo-albumins or phospho-globulins are insoluble in water and acids, but soluble in alkalies, and have an acid reac'tiOn . " Caseinogen " (after W . D . Halliburton) is the chief albumin of milk; its composition varies with the animal . It is insoluble in water, while its salts are readily soluble .

" Eucasein-'" is` the ammonium salt; " nutrose " and " plasmon " are

sodium salts . By the rennet ferment caseinogen is converted into casein, a substance resembling caseinogen in being soluble''in water, but differing in having an insoluble calcium salt . The formation of casein involves the curdling of milk . Other phosphoglobulins are vitelline, found in the yolk of hens' eggs, and ichthulin, found in the eggs of fish . Histone.r lre class of albumins soluble in water and acids, but essentially basic in character; hence they are precipitated by alkalies . It is remarkable that many histones are soluble in an 'excess df alkali . They do not exist in a free state, but in combination with a " prosthetic group " (after A . Kossel) they give rise to important cell constituents—haemoglobin, nucleo-proteids &c, " Thymus histone " occurs in the thymus gland; globin occurs in combination as haemoglobin; other histones have been extracted from the red blood corpuscles of the goose and the testes of fishes and other animals . The protamines are a-well= characterized class of albumins found in the ripe spermatozoa' of fishes . Albumoses and Peptones.—The primary products of the dissociation of albumins are the abumoses,. characterized by not being coagulable by heat, more soluble than the albumins, having a far less complex composition, and `eApable of being"salted out " by certain salts, and the peptones, similar to albumoses but not capable of being " salted out "; moreover, peptones are less complex than albumoses . By further decomposition peptones yield peptides, a certain number of which have been synthesized by Emil Fischer and his collaborators . Albumoses and peptones are white powders, readily soluble in water, with the exception of the hetero-albumoses—a subdivision of primary albumoses .

They give the biuret and xanthoproteic reactions, and

form salts with both acids and bases . Albumoses and peptones are obtained by peptic digestion, the latter being termed peptic-peptones; tryptic digestion also produces peptones . Acids and moist heat induce similar changes . Proteids.—These substances are combinations of one or more albumins with a radical of an essentially different nature, termed by Kossel a " prosthetic group." It is convenient to classify proteids by those groups . " Nucleo-proteids," constituents of the cell-nucleus, are combinations of albumins and nucleic acid; they always contain iron . They are loose, white, non-hygroscopic powders, soluble in water and salt solutions, and have an acid reaction; they give the colour reactions of albumins . Nucleic acid is at present of unknown constitution; decomposition products are: phosphoric acid, uracil or 2.6-dioxy-pyrimidin,l cytosin or 2-oxy-6-amino-pyrimidin, thymin . (nucleosin) or 2.6-dioxy-5-methyl pyrimidin hypoxanthin' or 6-oxypurin, xanthin or 2.6-dioxypurin, adenine or 6 amino-purin, guanine or 2-amino-6-oxypurin, pentoses (1-xylose), laevulinic acid, ammonia, etc . The nucleic acids vary with the source of the proteids, there being considerable differences in chemical composition . In generA,i they are white, loose powders, slightly soluble in cold water, more soluble in hot water; they are precipitated by mineral acids, but dissolve in an excess . They are dextrorotatory, and the specific rotation is numerically greater than that of albumin; hence the proteids are, in general, dextrorotatory . An important nucleo-proteid is haemoglobulin or haemoglobin, the colouring matter of the red blood corpuscles of vertebrates; a related substance, haemocyanin, in which the iron of haemoglobin is replaced by copper, occurs in the blood of cephalopods and crayfish .

Haemoglobin is composed of a basic albumin and an acid substance haematin; it combines readily with oxygen, carbon dioxide and carbon monoxide to form loose compounds (see NuTRITtoN) . It coagulates at 64° . By a dilute acid haemoglobin is decomposed into globin, and " haematin," a

ferri-pyrrol derivative of the probable formula C34H34N4FeO5i under certain conditions the iron-free " haematoporphyrin " is obtained . This last substance may be reduced to mesoporphyrin, C34Hn8O4N4, which by further reduction gives haemopyrrol, CaH13N, possibly methyl-propyl-pyrrol or butyl-pyrrol . Other derivatives are haemin, haemochromogen and the haematinic acids . " Glyco-proteids " differ from nucleo-proteids in containing a carbohydrate radical, which is liberated only by boiling with mineral acids or alkalies . The mucins and mucoids belong to this group; they are acid and contain no phosphorus; they give the albumin colour reactions but are not coagulated by heat . Mucins occur in most of the slimy fluids of the body; they vary in composition with their source . Mucoids resemble mucins in their composition and reactions, but differ, in general, in their physical properties . They occur in tendons, bones and cartilage . The " phospho-glyco-proteids " resemble the mucins and mucoids in containing a carbohydrate residue, but differ in containing phosphorus . Ichthulin (see above) may be placed in this group; " helico-proteid," found in the serous gland of Helix pomatia, the vineyard snail, also belongs here .

Abbuminoids is the anatomical name given to albuminous substances forming the connective tissues . Chemically they resemble the albumins, being split up by acids or ferments into albumoses, peptones and amino-acids, forming salts, and giving N=CB ' The pyrimidin

ring is numbered 2C ,C5 . For the purin ring, see PuxrN . N—C 4 4the same colour reactions . They are quite insoluble in water and in salt solutions, and difficultly soluble in dilute acids and alkalies . Typical albuminoids are gelatin, keratin, elastin, fibroin, spongin and conchiolin . " Collagen " (Gr. ichXXa, glue, and root yev- of yevvaeuv, to produce, ytyveuOat, to become), the ground-substance of bones and tissues, is decomposed by boiling water or on warming with acids into substances named gelatin, glutin or glue . Gelatin forms a white amorphous powder; the commercial product, however, generally forms glassy plates . The decomposition products are generally the same as with the general albumin; it gives the biuret reaction; forms salts with acids and alkalies, but is essentially acid in nature . Immersed in cold water gelatin does not dissolve but swells up; it dissolves readily in hot water, forming, according to the quantity present, a thick jelly which solidifies to a hard mass on cooling (the " glue " of the wood-worker), or a thin jelly (used in cookery) . Gelatin occurs also in the cornea and the sclerotic coat of the eye; and in fish scales, the latter containing 8o% of collagen, and 20% of ichthylepidin, a substance differing from gelatin in giving a well-marked Millon's reaction . Keratin (Gr .

Kipas, a

horn), the chief constituent of horny material, occurs in hair, nails, hoofs and feathers . It is quite insoluble in water, dilute acids and alkalies . Related to this substance are "neuro-keratin," found in the medullary sheath of nerves, and " gorgonin," the matrix of the axial skeleton of the coral Gorgonio Cavolinii . Elastin occurs either as thick strands or as membranes; it. constitutes the " elastic tissue " of the anatomist . Its insolubility is much the same as keratin . "Fibroin " and silk-glue or sericin occur in natural silk fibres . Fibroin is insoluble in water, acids and alkalies; silk-glue resembles gelatin in its solubility, but it is less readily gelatinized . " Spongin," the matrix of bath-sponge, is insoluble in water and dilute acids, but soluble in concentrated mineral acids . " Conchiolin," the matrix of shells of the mollusca, is only slightly soluble in acids . " Cornein " forms the framework of corals . " Amyloid " occurs as a pathological product, and also in the healthy aorta and in old cartilage . It is an albumin, and not a carbohydrate as was formerly held; and gives most of the colour reactions of albumins .

It forms shiny, homogeneous masses, quite insoluble in cold water and in salt solutions, but soluble in alkalies . The albumoids include, according to Cohnheim, substances which possess certain properties in common, but differ from the preceding groups . In general they resemble coagulated albumin, and also the gelatin-yielding tissues, but they themselves do not yield gelatin . Colouring matters derived from albumins include the " melanins " (Gr. ykX as,

black), substances which differ very considerably in composition, the sulphur and iron content being by no means constant; they do not give the reactions of albumins . The black colouring matter of hair, the skin of negroes, and of the ink bag of Sepia have been examined . Melanins obtained from tumours form black, shiny masses; they are insoluble in water, neutral salt solutions, dilute acids and in the common organic solvents .