300 



M. W. ANDREWS AND J. SIKORSKI 



In an ultrathin section through a cell wall of date 

 endosperm the whole wall appears to be built up of 

 small grains (fig. I ). However, if by chance a section 

 through a swollen cell wall is obtained, microfibrils 

 are visible between the swollen layers of the wall 

 (fig. 2). It does not seem likely that they are of a 

 cellulosic nature, since, as Reiss (5) has found, the 

 whole thick central layer of the wall disappears when 

 the seeds germinate. 



To obtain an answer to the question whether there 

 exists a morhological difference between the man- 

 nans A and B, the finely ground endosperm of date 

 seeds was extracted with acetone and ether, macer- 

 ated with acetic acid/hydrogen peroxide (1:1) and 

 treated with a defibrator of the Turmix type and/or 

 with ultrasonic waves. This material was found under 

 the electron microscope to consist of two morpho- 

 logically different components. There are small grains 

 visible which are often aggregated to greater parti- 

 cles and there is also about the same quantity of 

 microfibrils (fig. 3). However, the microfibrils are 

 mostly covered by the grains and therefore appear 

 to be present in a smaller quantity. Chemical analysis 

 of the sample yielded, after hydrolysis, 15 "„ glucose 

 with traces of galactose and 85 °o mannose. The 

 mannan A was extracted from this sample with 

 7 % potassium hydroxide at room temperature. 

 This specimen free of mannan A appeared in the 

 electron microscope to consist of microfibrils only. 

 The small grains and their aggregates had disappea- 

 red almost completely (fig. 4). It follows that the 

 grains visible in fig. 3 are identical with the low 

 molecular weight mannan A. If the latter is precipi- 

 tated again from the extract it forms nearly cubic 

 particles with a diameter of about 1 //. An ultrathin 

 section through such a particle shows that it is built 

 up of small grains very similar to those of the mannan 

 A in its native state. 



The specimen that is shown in fig. 4 gave on 

 paperchromatographic analysis 39 % glucose and 

 61 % mannose. Results analogous to those from date 



cells have been obtained with ivory nuts. After 

 extraction with 7 % potassium hydroxide an ivory 

 nut sample yielded on chemical analysis 20 °o cellu- 

 lose and 80 "o mannan and also appeared in the 

 electron microscope to consist only of microfibrils. 

 This provides evidence that the high molecular 

 weight mannan B is built up of microfibrils analogous 

 to those of cellulose. Their width also seems to be 

 of the same size. At present it is difficult to say 

 whether there are pure mannan or only mixed 

 mannan/cellulose microfibrils. However, the latter 

 might be less probable because the mannan B can, 

 after prehydrolysis of the material with 1 % hydro- 

 chloric acid, be completely extracted with 24°o potas- 

 sium hydroxide, whilst the cellulose is resistant to 

 this treatment. This would hardly be possible if 

 there were mixed crystallites of 80 % mannan and 

 20 % cellulose. 



It might be noted that without prehydrolysis 

 mannan B cannot be extracted with 24 "o potassium 

 hydroxide at room temperature. A sample that was 

 first extracted with 7 ^o, then with 14 "o, 18 % and 

 finally during three days with 24 % potassium 

 hydroxide still yielded 77 '^o mannan. 



The conclusion of all these observations can only 

 be that the mannan B builds up the framework 

 of the cell walls of palm seeds in the form of 

 microfibrils quite analogous to the cellulose in other 

 plant cell walls. The mannan A on the contrary 

 lies incrusted within the framework of the mannan 

 B. This might possibly be an indication that the 

 resistant hemicelluloses of woody fibers also form 

 microfibrils. 



References 



1. AspiNALL, G. O., Hirst, E. L., Percival, E. G. V., and 



Williamson, I. R., /. Chem. Soc. 3184 (1953). 



2. Klages, P.. Liebigs Ann. Chem. 509, 159 (1934). 



3. — Ibid. 512, 185 (1934). 



4. LuDTKE, M., Liebigs Ann. Chem. 456, 201 (1927). 



5. Reiss, R.,j9e/-. 22, 609(1889). 



A Contribution to the Structure of Keratin 

 M. W. Andrews and J. Sikorski 



Textile Physics Laboratory, Department of Textile Industries, 

 University of Leeds 



In spite of great advances in the study of keratin 

 structure, during the last quarter of a century or so, 

 it is, nevertheless, evident that the information 

 available is still very incomplete. 



Thus, at the molecular level the difficulties to 

 establish a convincing relation between the results 

 of chemical analyses and x-ray diffraction data, are 

 as many as they are formidable (I, 2, 9. II) and 



there can be little doubt that the ambiguity (except 

 in the case of cortical cells: Woods (15)) about the 

 individual effect of various histological components 

 of keratin fibres, on the x-ray diffraction pattern, 

 could be considered as, at least, a contributory 

 factor in this respect. Recent discoveries of the bi- 

 lateral structure in crimpy wool fibres (8, 10) call, 

 among other questions, for the consideration of 



