Publications by authors named "O L Sponsler"

6 Publications

  • Page 1 of 1

MECHANISM OF CELL WALL FORMATION.

Authors:
O L Sponsler

Plant Physiol 1929 Jul;4(3):329-36

Organomolecular Investigations, University of California at Los Angeles.

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC440065PMC
http://dx.doi.org/10.1104/pp.4.3.329DOI Listing
July 1929

MOLECULAR STRUCTURE OF PLANT FIBERS DETERMINED BY X-RAYS.

Authors:
O L Sponsler

J Gen Physiol 1926 May;9(5):677-95

University of California, Southern Branch, Los Angeles.

It has been shown that the wall of the plant fiber is probably built up of unit groups of atoms which have assumed the form of a space lattice. The elementary cell of the lattice is an orthorhombic structure with the dimensions 6.10 x 5.40 x 10.30 A.u., and contains two unit groups equal in size to two C(6)H(10)O(5) groups. The crystallographic unit cell would contain 4 of these elementary cells and would be represented by Fig. 9 rather than by Fig. 3. The groups of atoms, C(6)H(10)O(5), are arranged in parallel chains running lengthwise of the fiber. In each chain the odd numbered groups have a different orientation from the even numbered. The chains, parallel to one another are spaced 6.10 A.u. in one direction and 5.40 A.u. at right angles to that. In these two directions the odd numbered chains also would have a different orientation from the even numbered. On account of the cylindrical shape of the fiber, the elementary cells are arranged in the form of concentric cylinders or layers. The dimensions of the fibers are such that the fiber wall is about 40,000 elementary cells in thickness, or in other words, the fiber is composed of that many concentric layers. If it could be magnified sufficiently, a cross-section of a fiber would show the end view of each cylinder as a dotted circle. The dots, representing the unit groups of atoms, would have considerable uniformity of spacing in both the tangential and the radial directions, 6.10 A.u. in one and 5.40 A.u. in the other. The structure could not be as rigidly exact as might be inferred, since the wall is deposited more or less rhythmically during a period of several days or weeks* in which adjustments in the arrangement of the unit groups undoubtedly occur. It is common knowledge that the fibers, under the microscope, rarely appear as true circles on cross-section; usually they appear as irregular, many-sided polygons and the wall thickness is normally uneven. For our purpose it is simpler to think of the fiber as composed of concentric cylinders with diameters so large in proportion to the size of the unit groups that in relatively large segments they closely approach the parallelism of the planes of a rectangular lattice, sufficiently close to be capable of producing diffraction patterns. Although these conclusions seem to be in agreement with the diffraction patterns obtained from various positions of a bundle of approximately parallel fibers, the fact must not be overlooked that the structure cannot be proved with as great certainty as can the structure of a well formed crystal. The very nature of the fiber, its cylindrical shape, and the many internal adjustments which must take place, militate against a clean-cut demonstration. Models, made more or less to scale, were used in working out this structure. The unit group was constructed according to Irvine's suggestion that all the groups are glucose residues. An intensive study is now under way in which an attempt is being made to bring the models into agreement with the chemical and physical properties of the cellulose fibers and with the diffraction patterns. A report on that part of the work will soon be submitted for publication.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2140850PMC
http://dx.doi.org/10.1085/jgp.9.5.677DOI Listing
May 1926

X-RAY DIFFRACTION PATTERNS FROM PLANT MATERIALS.

Authors:
O L Sponsler

Science 1925 Dec;62(1615):547-8

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http://dx.doi.org/10.1126/science.62.1615.547DOI Listing
December 1925

X-RAY DIFFRACTION PATTERNS FROM PLANT FIBERS.

Authors:
O L Sponsler

J Gen Physiol 1925 Nov;9(2):221-33

University of California, Southern Branch, Los Angeles.

The rather long discussion just given seemed necessary in order to establish certain points before attempting to develop the lattice structure and before working out the identity of the structural unit of the ramie fiber. 1. Certain planes, 6.10, 5.40, 3.98, etc., as given in Table I, run lengthwise of the fiber; that is, they are parallel to the long axis. 2. These planes are in agreement with the assumption that one set, either the 6.10 or the 5.40 is tangential to the fiber and forms concentric cylinders, with the long axis of the fiber as the long axis of the cylinders; the other set, either the 5.40 or the 6.10. cuts the former at right angles and therefore its planes are radial with respect to the fiber, theoretically all of them meeting at the long axis, as indicated in the cross-section of a fiber in Fig. 3. 3. Other planes, 5.15, 3.40, 2.58, etc., as given in Table III, are transverse planes which form right angles with the long axis and therefore with the planes of Table I. 4. All of the planes are composed of reflecting units, probably groups of atoms, located at the intersections of the planes. This being the case, other reflecting planes must occur at other angles to the long axis. This prediction is verified by the lines given in Table IV. 5. The structural units in the wall of the fiber thus form a space lattice, the elementary cell of which is an orthorhombic structure. 6. Comparatively little can be said as yet concerning the structural unit. The unit is very probably composed of a group of atoms which are more or less closely packed together. If the groups were visible they would appear, in a cross-section of a fiber, as closely packed groups of atoms, 6.10 A.u. from center to center of groups in one direction, and 5.40 A.u. at right angles to that. In a longitudinal section, however, they would appear less compact and might even lose the appearance of groups in forming long strings of atoms which would extend lengthwise of the fiber. By establishing the positions of the planes in the wall of the fiber, as in Tables I, III, and IV, it would seem that all dimensions of the elementary cell, and the size and character of the structural unit, could be determined. Work along these lines is now in progress.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2140797PMC
http://dx.doi.org/10.1085/jgp.9.2.221DOI Listing
November 1925

STRUCTURAL UNITS OF STARCH DETERMINED BY X-RAY CRYSTAL STRUCTURE METHOD.

Authors:
O L Sponsler

J Gen Physiol 1923 Jul;5(6):757-76

University of California, Southern Branch, Los Angeles.

A few brief statements summarizing the foregoing conclusions may make a picture of the structure of the starch grain somewhat clearer. 1. The presence of lines on the negatives indicates a regular arrangement of the planes of atoms. 2. The lines are in close agreement with lines which would be produced by a lattice of the tetragonal system, the elementary cell of which is a square prism with the dimensions 5.94 x 5.94 x 5.05 A.u. 3. The unit of the lattice occupies a space equal to the volume of the starch group, C(6)H(10)O(5). 4. The large number of atoms in the unit makes it highly probable that principal planes and secondary planes of atoms occur for every reflecting position. 5. The effect of the secondary upon the principal planes may readily account for the differences in the density of the lines produced on the negatives. 6. From theoretical considerations, reflections, such as those obtained, would occur if starch grains were built up of concentric layers of units. 7. Two other factors which might affect the density of the lines are thermal agitation and the curvature of the concentric layers. 8. A model of the starch group was constructed to scale based on the accepted sizes of the atoms involved and upon rather meager chemical evidence. The model apparently fulfills the requirements necessary to produce reflections such as were obtained. 9. The model fits the elementary cell loosely enough to suggest a low density and to allow for considerable thermal movement. At the same time, parts of it approach the faces of the cell closely enough to make cohesion seem possible. 10. The model makes clearer the basis for the assumption that reflection from certain positions would be stronger than from others. If the interpretation of the data is correct and if the assumptions made are sound, then the starch grain is built up of units arranged in concentric layers, and the units are groups of atoms, each containing 6 carbon, 10 hydrogen, and 5 oxygen atoms. Such a structure is certainly not an amorphous structure, and on the other hand it is not crystalline in the common sense of the term. Parts of the grain, it is true, act as crystals in that for certain distances the layers of units are in planes, but taken as a whole the layers are curved. As to the validity of the conclusions, those pertaining to the type of lattice and to the size of the unit may be accepted as sound in our present knowledge of x-rays and crystal structure; those, however, pertaining to the nature and the spherical arrangement of the units, while they seem convincing, need the support of further investigation into the various structures deposited by living protoplasm. In conclusion, the assumption that the units form a sort of spherical space lattice, gives a picture of the starch grain which leads us to ponder over the nature of the activity in protoplasm when it is depositing solid substances. Starch, cellulose, and pectic bodies are about the only solid deposits made directly by the living substance of plants, and all three have the same proportional formula, C(6)H(10)O(5). Investigations, as yet incomplete, indicate that cellulose also consists of a regular arrangement of C(6)H(10)O(5) groups, each acting as a unit, but the spacing (6.14 x 6.14 x 5.55) is slightly different from that of starch. Pectin has not been studied. Protoplasm may be thought of as being composed of molecules of many different sizes, polypeptides, or even proteins forming the larger, and amino-acids the smaller, if water and electrolytes are ignored. The smaller molecules, such as those of the amino-acid, leucine, are approximately equal in size to the C(6)H(10)O(5) group of starch. That being the case, what can be the state of affairs at the interface when the starch particles are being deposited? Is it probable that protoplasm is homogeneous to the extent of being able to deposit these particles at 6 A.u. intervals? From quite another view-point a clear picture of the units of structure and their arrangement in cellulose should give a new point of attack on the many problems connected with osmosis. And from still a different view-point, it might lead perhaps, to a solution of problems connected with swelling. Another line of thought is suggested by the uniformity of the groups in the starch grain. Since the C(6)H(10)O(5) group occurs as an individual unit, one is inclined to suspect that it is really the molecule. Generally the starch molecule is considered to be very large, to be composed of several dozens of such groups, and to have a molecular weight of 7,000 or much more. No one figure, however, seems satisfactory to the different authorities. There is already at hand considerable evidence which will be assembled in a later paper favoring the single group, C(6)H(10)O(5), as the molecule. Finally, problems in polarized light may receive more satisfactory explanations through a clearer notion of the molecular structure of the carbohydrates.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2140597PMC
http://dx.doi.org/10.1085/jgp.5.6.757DOI Listing
July 1923