. The cell and protoplasm ... Cells; Protoplasm; Cytology; Cytoplasm. 176 THE CELL AND PROTOPLASM Lomax 1935), giving them a uniformity of position from which a diffraction pattern may be obtained with X-rays, somewhat similar to that from a fiber "where the long chains are extended full length and ar- ranged in parallel fashion, as has been shown to be the case in silk. In silk they are separated from one another laterally at uniform distances of A in one direc- tion and about A in another. These di- mensions are slightly smaller in silk than the corresponding dimensions of most
. The cell and protoplasm ... Cells; Protoplasm; Cytology; Cytoplasm. 176 THE CELL AND PROTOPLASM Lomax 1935), giving them a uniformity of position from which a diffraction pattern may be obtained with X-rays, somewhat similar to that from a fiber "where the long chains are extended full length and ar- ranged in parallel fashion, as has been shown to be the case in silk. In silk they are separated from one another laterally at uniform distances of A in one direc- tion and about A in another. These di- mensions are slightly smaller in silk than the corresponding dimensions of most pro- teins, where they vary over only a narrow range—from A to A for the thick- ness of the chain, as illustrated in Fig. 4, and from 9 A to 12 A as extremes for the width. The width is obviously an average depending upon the proportion of long and short side chains, as may be seen in Fig. 3. Averages taken for a protein chain for general use are about A for thickness and A for width. See Table VI in which these dimensions are given for many proteins. There are three ways of arriving at these two dimensions; one is by actual measure- ments of width and thickness, on a model made to scale from dimensions of the com- ponent atoms; a second way is from X-ray diffraction patterns; and a third is from computations involving density and molec- TABLE V Comparison op Width of Various Protein Mole- cules AS Obtained by Different Methods Protein I Avei'. mol. wt. of resi- dues Keratin (wool) Edestin (hemp) Lactal- bnmin Zein (corn) Egg albumin Casein Gliadin (wheat) Gelatin Silk fibroin II Aver. length of resi- dues III Width of i^rotein molecule From mol. wt. and spec, gravity IV From residue length V 114 a a A 118 128 113 124 122 121 95 73 From X-ray data VI a Fig. 4. An end view of a protein nuidi The verticnl tliicl<
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Keywords: ., bookauthoramericanassociation, bookcentury1900, booksubjectcells
