The faces of the crystal were kept parallel by observing interference colors of the crystal in between. Thicknesses were determined by measuring the retardation of the crystal under crossed Nicols with a quartz wedge and monochromator. As shown in the figure, the prisms have corresponding faces that are nearly perpendicular to the optical axis of the instrument.
The dotted line waves vibrate at right angles to the plane of the paper. The quartz wedge has its fast jet component above the fast jet component of the crystal. The crystal was oriented so that its fast component coincides with the slow component of the quartz wedge.
For first-order work, the quartz delay was reproduced within 2 to 3 rrw. The compounds are usually 10 M in the crystalline state and have molar absorptivities of the order of . The block was oriented so that the (001) face (the plane of the molecular layers) was in the plane of the cutting edge.
Shave 10 to 20 1-L of the crystal; this leaves an optically smooth face on the crystal.
THIN
A uniform layer of the solution was spread on a quartz cover::3lip to give a plastic film of about 10 IJ.• The solution evaporated and the film was pumped along. 9-Methyladenine~. The crystal absorption spectra of 9-methyladenine in the {00 1) plane are shown in Figure 13 and Table IV. The absorption spectrum along the b-axis::i (perpendicular to the molecular planes) of the Hoogsteen dimer is shown in Figure 17.
Therefore, the directions of the passing moment of these rmolecules are the same • The orientation of the hydrogen bonded pair, molecules (3) and (4), is obtained from (1) and (2) by a reflection in a plane perpendicular to b. - axis. The calculated interaction energy is .:t 200 em -1 For the large number of aggregated molecules (several hundreds) the interaction doubles to!, 400 em -l • The half-width of the vibrational band for the solution spectrum is 3720 cm -1 . To the extent that x i is close to 90•, the ratios of the principal axes serve as approximations for R and R.
Both of these values are in strong disagreement with the .. oscillator directions determined by the assignment for '{ = 95•. 2, the molar absorption of the two self-oscillator8 responsible for the absorption of the crystal. Thus the first order • free intensity. molecule is the same as for the molecule in solution.
Absorption spectra of 9-methyladenine in different environments. abeorptivities for the two main directions in the plane of. Polarization experiments show that the direction is 161°, which is a discrepancy of 22•. The absorption perpendicular to {010) for the Hoogsteen dimer is probably due to ton - n * transitions in the purine moiety. 7 provides a place for the transition, which is expected to be blue of the other n-1'1 * transitions.
It is estimated that the eccentricity of the polarized light is :mi ty and that the solid angle is uniformly filled with light.
III =
The structure will also hopefully resolve the issue regarding the direction of the transition moment for the strong component of the first ultraviolet absorption. I have assumed that the two pairs of four molecules per unit cell are hydrogen bonded by N. The arrow above a molecule is believed to be the direction of the transition moment.).
The current intermolecular spacings as now shown in the unit cell are not acceptable. A 5 bond closer to the b-axis increases the separation of adjacent methyl groups and also increases N. It is, however, useful in determining the approximate orientation of the 9-methyladenine molecules in the unit cell.
The dependence on the rotor speed suggests that the molecules are oriented by the effect of the centrifugal field. Thus, intermolecular interactions as well as the centrifugal field effect appear to be important factors for the rate dependence. In the first two possibilities, both dichroism and birefringence of the bulb would develop with the field strength.
The rotation of the polarization plane must be measured accurately so that the polarizer can be properly oriented. The orientations of the two molecules per unit cell in the orthorhombic crystal are pleasantly simple. These types of polarization studies will contribute to the understanding of the intensity obtained by the symmetry.
This case corresponds to bars falling on the cutting lines with bar axes parallel to the z-direction and in the plane of the knife edges. From osmotic pressure n'leasurernents, for example, as a function of the slice interval, a plot of 1/ M versus 1/. For model I, it is assumed that DNA has polarity in the genetic sense and that one end of the molecule is required for incorporation.
Pes)
Re Slllta shows that the number average molecular weight experiment is more suitable for simple interpretation. The transcendental expression for the weighted average length requires careful experimentation and knowledge of L. If one can independently determine the linear density of the polymer, the curve will be 1/M vs. 1/s.
The point here is that cutting experiments cannot determine a unique distribution for the rods in the fiber. It is proposed that the latter analysis be used to process data from the density gradient. For certain conditions, the resolution of two Gaussians with arbitrary amplitudes and bandwidths was considered and solved (2).
One condition was that the respective maxima of the two Gaussians were distinct; the other that the distribution has at least four inflection points, one Gaussian manifested as a shoulder. Although a system is "unresolved" by our cl"itery, if one has a system in which he knows there are two species, then the overall resolution of the corresponding Gaussians is in principle solvable. A solution for the width case of equal band ;;, but different amplitudes and positions are described below.
The case of equal amplitudes and bandwidths but different positions is solved and a generalized least squares analysis is performed. To the extent that each of the two strands !>as a different density, the strands will move to their respective densities. The single Gaussian distribution for the native molecule will now be expanded and become a sum of t.lte two characteristic Gaussians for each string.
To perform a least squares analysis for this experiment, the original DNA must be very homogeneous and strand breaking due to Jith base action must be minimal. The analysis of the two Gaussians with equal amplitudes and bandwidths is now presented. Since the two Gaussians are equal, the centroid position i will be the origin of the system, such that.
