CIRcle cell spectra

In order to test whether our CIRcle cell spectra were dominated by adsorbed protein or protein in solution, we ran spectra of a series of lysozyme solutions ranging in concentration from 0.12 to 102. The IR response of the amide I and II bands at 1653 and 1543 cm-1 is nearly linear with concentration between 5 and 102 lysozyme. However, the IR intensities change very little between 0.1 and 12, strongly suggesting that most of the signal we observe at 0.12 concentration is due to adsorbed lysozyme. Since our study of subtilisin BPN was done at 0.012, we are almost certainly observing only adsorbed species in our ATR spectra. 

An ATR device that has become quite popular is a commercial cell, the ATR Circle Cell (Spectra-Tech), that has a large effective surface area that is approximately 7-8 times greater than that of the ordinary rectangular IRS (ATR) crystal (Fig. 3.12). 

Figure 17. (Top) The absorbance spectrum of a levitated bubble of LGP1845. (Bottom) The Circle Cell spectrum of LGP1845. Because of the longer pathlength, the bubble spectrum is more intense, but the spectral features match well between the two.

Figure 3. A series of spectra of 100 ppm subtilisin BPN from 6 to 180 minutes after injection into the CIRcle cell. The solvent spectrum has been subtracted.

Figure 11. Quantum monodromy in the spectrum of the quadratic Hamiltonian of Eq. (38). The solid lines indicate relative equilibria. Filled circles mark the eigenvalues of the most stable isomer and those above the relevant effective potential barrier in Fig. 8. Open circles indicate interpenetrating eigenvalues of the secondary isomer. The transported unit cell moves over the hlled circle lattice, around the curved fold line connecting the two spectra.

The IRE of the Prism Cell was coated with a layer of hydrocarbon "model soil" in the same way as was done in earlier work with the CIRCLE (5.12). The IRE is withdrawn mechanically from the solution of the hydrocarbon of interest (2-4 wt.% in hexane) at a slow, controlled rate. The hexane flashes off, leaving a layer of hydrocarbon behind. By varying the withdrawal rate and the concentration of the hydrocarbon, layers of varying thicknesses, as judged by the intensity of the bands of the hydrocarbon spectrum, can be obtained. 

For example, Fig. 6b shows the raw SFG spectrum of CO on Pt(l 11) in the presence of 200 mbar of CO at 300 K (open circles) together with the applied gas-phase compensation curve (solid line) and the corrected spectrum (black dots). To prevent the undesired attenuation of the IR beam by atmospheric CO2 and water before entering the SFG cell, all beam lines were encapsulated and purged with dry nitrogen. 

The relation between particle size distribution and NMR spectrum has been modeled in the NMR layer model 156). Here I describe a simple version a more elaborate one has been proposed by Makowka et al. 157). We start by constructing size histograms from TEM micrographs. To do this, it is customary to consider the images on the inicrograph as circles with diameter d equal to that of effectively spherical metal particles that cause the image. Furthermore, this diameter is converted to the total number N y of atoms in the particle by (for the FCC structure, four atoms per unit cell)... 

Fig.31 I-V measurements of P3HT PCBM solar cells under 80mW/cm AM 1.5 solar spectrum simulation (light). The photocurrent and the diode characteristics improved from untreated (U, squares) over thermal annealing (T, open circles) to thermal annealing in combination with the application of external voltage (T + I, open triangles), (Reproduced with permission from [172], 2003, Wiley-VCH)...

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