Chackraburtty, D M

Chakravarti, B

English

IACS Institutional Repository

AN X-RA Y STUDY OF SOME LEATHERSl> M. CHACKKABUKTTV anj> B CHAKKAVARTIJjJCrATlTMKNT OK (JlSNEKAi. I'UYHICH AND X-UAYSX.ssorr\'i’ion kok thk (iLJ/riVATioiv ok Sciknce, .lAA Am'im,VIAUJ'J’TA[Ut'A mV, M a t/  1."), HJf)?)Waio IABSTRACT Tliw .sjnu ni^ h. «»1 » lui diffum' niton,so bund of Homo Jouthor wumplos woio iiioaHurod. Jl was obaorvocl that blio H))af;iiigH mojo \nryuig fioin Hamjdo to sainplo. Tho ^■u^ utlOIls HIV rxplaiiM'd on llio biisiH of Pauling h model of collagoii-Kclatin Htrucfcmo.I N T K t) U L: U 'V 1 () Xriie outHtaiKliJig works on Jeathers and skins which arc cJassitied nmicr ( ollagcji-jrclatin protion ^roup wore mainly conliiicd to the measurement, ol JiUTTflional and mjnatorial reflectjons and the m tcrpretatnm  of such rcflec.tions H was ponded oid hy Bear (1D4-4) tliat the principal jnendiomd arc was varynifr (rom 2S2 A to 2 tlOA, and the principal equatorial refiection helwecii 10.4 A to 15.5 A The variation of the equatonal retlcction was accounted for bu t the variation ol spacings ol meridional lellection has nevci been seriously lookerl into. Pauling (1U51), however, pmjioscd a model ol the jiolypeptide chains in coJlagen-geJlatiii protein with special lefeieiu-c to dried tendon for which he accepted the value ol the jniiicipaJ eijuatonal rcltcctioii as 10.4A and the men- dional j-dfection as 2 8bA and set up a satisfactory sti-iictiire by assuming alter­nation of two CIS groups and a trails giouj) in polypeptide ciuihi and three such folypeptide chains coiled into helix, the binding bet ween the ehains being achieved l)V intramole(‘ujar hydiogen bonds. 1^he coihiig ol Ibe ehains were achieved a t the a-carhon atom, Tim im portant features of such structure are (1) the dihedral angle at these carhon atoms is 97 , (2) the helix lormod by a single eiiam of collagen nmleciile lias nearly a 9--fold screw axis ol'sym melrv and (:}) the value toi (.-N -(. in polypeptide chain is J2;^‘ A sot of co-ordinates weie derived foi different atoms on the above considerations and the denvalioii of the form bictor F led lo the calculated intensity and spaeiiigs of (orlain haiids The im- poj tiiuf diffuse mltmse band o(‘ some eonsifleraliie intensity was ealeulated to be 4 72A.K X I' K K I M 4J N 'r  A L OB ,S JO p, A 'I' I O NT liie \erilieation of the sfniefure reipiires an aeenrale measurement, of the band spacing partienlavly Ibal of the calculated intense hand at 4.72A For dried (endoM onl> tl.c ohseived spac-ing of such baud was reported as 4.4 A byU)Indian Jouinal oj Physics, \o I  \X X IJ  No iH A K R A BU R TTY  & C H A K R A V A R T l jIarI'lg- 7I'lg 2Pu- 4Fig. (JX-ray photographs of Icatlipr srunplesA n  X - r a y  S tu d y  o f  Home LejithernAatbury (1940) and 4.37A by Paiilni^ and (brey (1951) In (ho proHeid iuveaii- o;ation we have (‘oneentrated our attention on the measuromenl of tlie dilTuHo baud ill different sampleH of loaUier with the idea of eorielating the oliaerved and calculated spacings blach leather or skin Hpeciiuen was cut into tliin stri]) and inoujitod on a frame. Thia frame was in tiuni mounted on a goniometer head of X-ray camera and pictures were taken in (kiKa and CoKa radiations whieli showed bands and in several cases faint lines of chemicals like NaCl used during tanning Using the observed 20U reflection of NaUl as the internal standard in some cases, the spacing of the diffuse band was calculated and some of the results were verified by taking jihotometric rec.ords Foi accuirate measurement some of the X)ietnres were taken in cobalt radiation instead of coppei ladiation. The results are tabulated in 1’able 1 and the pictures arc shown seyiaiately iii Plato 1.TABl.U 1SamploK ( 'umera radniK Kiuliatiou usedSpacing ol‘ thr diffiiHo bundSampU) 1 rjn.s. (\j])pei 4 3:> ASample 11 3 eniK. (Copper 1 -17 ASample 111 3 rms. (. 'oppei' 4 33 ASample IN' 1.13 cnis CopyKT 4 49 ASample V r 56 emu t 'oppei 4 .32  ASample 4 55 cmH (iobalt 4 .44  ASample VII 4 .13  cniH (ioball, 4 .74  A1) 1 S U S S 1 0 N OK H E H E S E L TJt is djflticult to :(ind out a svslcmatic correlation between the observed valueand calciilateil value 4.72A. Tn samples II, IV, VI and VJl the observetl results are nearer to the calculated value, but in others the observed values are too lo\^  To account for the low values we have assumed certain distortions and deviations ni the structure already proposed. Although we arc unable to establish our views from the pictures obtained by us, we piedict th at it is possible to obtain the cal­culated band spacing lower than 4.72 A for a particular value of meridianal re­flection ranging between 2.82 A—2.90 A, but other than the value of 2.8CA. bearing, of course, in mind the variations of meridianal reflection reported by Bear (1944) Proportionally the D-N-fl angle must be changed slightly to account for (1) the helix formed by a single individual chain of collagen molecule to retain a 9-fold screw axis and (2) the intramolecular bonds binding the three12 D. M. Chackrab'urtty and B. Chakravartipolypeptide* ohaiii.s The other structural features will remain similar tf) th a t pro­posed in Paulina’s structure.A CK N 0  W I. K D(l M NT SThe authors express tlieir gratitude to Prof. B. N. Snvasl.ava for help, en­couragement and guidance ihroughonl the progress of the Avork.R E F E R E N C E SAstbui’y, AV T., H140, Jnm J n s i  S^o^ . L c a t h c i  T r m h n  ( l \ e m  , 24, 01).Boar R. S , 11144, Jmir. Aw, (Ihfin, tSnr., 66, 121)7Pauhiiff 1a aiifl Coroy E. B., ID-Al, Pto<, Arad of Sri , WashiKfion. 37, 272.

An X-Ray Study of Some Leathers

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An X-Ray Study of Some Leathers

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