Peak-decay analysis

Moore, R.M. and Walters, R.R., Peak-decay analysis of drug-protein dissociation rates, J. Chromatogr., 384, 91-103, 1987. 

Chen J, Schiel JE, Hage DS. Noncompetitive peak decay analysis of drug-protein dissociation by high-performance affinity chromatography. J Sep Sci 2009 32 1632-41. 

Yoo MJ, Hage DS. Use of peak decay analysis and affinity microcolumns containing silica monoliths for rapid determination of drug-protein dissociation rates. J Chromatogr A 2011 1218 2072-8. 

A 2 pmole quantity of the 62-kDa protein was digested in situ with trypsin in an excised polyacrylamide gel slice. The resulting peptides were resolved by reversed-phased HPLC. Peaks detected by HPLC were selected for further analysis by sequencing, LC-MS, and MALDI-TOF. One peak with a retention time at approximately 30.25 failed to yield an interpretable sequence. Upon further observation, the mass observed by LD-MS was consistent rvith the N-terminal residues of the 62-kDa protein with the addition of an N-terminal acetyl group. Post source decay analysis revealed that this peptide was indeed the predicted amino terminal tryptic peptide (Figure 3). All other peptide peaks matched various internal sequences of the r62-kDa protein. 

Attenuation occurs because the tensile release, which is traveling at an elastic longitudinal wave speed, Q, overtakes the tensile front traveling at a plastic wave speed Cp < Q. Assuming a pulse as shown in Fig. 8.10 with a stress rate in the tensile front and tensile release of a and b, respectively, an approximate analysis shows that the peak will decay by an amount... 

Fig. 11. Amide F thermal denaturation spectra for ribonuclease A as followed by FTIR (left) and VCD (right), which show the IR peak shifting from the dominant /3-sheet frequency (skewed with a maximum at 1635 cm-1) to the random coil frequency ( 1645-1650 cm-1) and the VCD shape changing from the W-pattern characteristic of an a + p structure to a broadened negative couplet typical of a more disordered coil form. The process clearly indicates loss of one form and gain of another while encompassing recognition of an intermediate form. (This is seen here most easily as the decay and growth back of the 1630 cm-1 VCD feature, but is more obvious after factor analysis of the data set, Fig. 15).

Fig. 1. Top Scheme of an inversion recovery experiment 5rielding the longitudinal relaxation time (inversion is achieved by mean of the (re) radiofrequency (rf) pulse, schematized by a filled vertical rectangle). Free induction decays (fid represented by a damped sine function) resulting from the (x/2) read pulse are subjected to a Fourier transform and lead to a series of spectra corresponding to the different t values (evolution period). Spectra are generally displayed with a shift between two consecutive values of t. The analysis of the amplitude evaluation of each peak from — Mq to Mq provides an accurate evaluation of T. Bottom the example concerns carbon-13 Tl of irans-crotonaldehyde with the following values (from left to right) 20.5 s, 19.8 s, 23.3 s, and 19.3 s.

The manner in which the RF pulse is applied is critical to NMR analysis. A very simplified pulse sequence is a combination of RF pulses, signals, and intervening periods of recovery, as illustrated in Figure 6.80. The main components of the pnlse sequence are the repetition time, TR, which is the time from the application of one RF pulse to the application of the next RF pulse (measured in milliseconds) and the echo time, TE. The repetition time determines the amount of relaxation that is allowed to occur between the end of one RF pulse and the application of the next. Therefore, the repetition time determines the amount of Ti relaxation that has occnrred. The echo time is the time from the application of the RF pnlse to the peak of the signal induced in the coil (also measured in milliseconds). The TE determines how much decay of transverse magnetization is allowed to occur before the signal is read. Therefore, TE controls the amount of T2 relaxation that has occnrred. 

The prediction of a heavy boson has received preliminary empirical support [92,96] from an anomaly in Z decay widths that points toward the existence of Z bosons with a mass of 812 GeV 1 33j [92,96] within the SO(l) grand unified field model, and a Higgs mechanism of 145 GeV4gj3. This suggests that a new massive neutral boson has been detected. Analysis of the hadronic peak cross sections obtained at LEP [96] implies a small amount of missing invisible width in Z decays. The effective number of massless neutrinos is 2.985 0.008, which is below the prediction of 3 by the standard model of electroweak interactions. The weak charge Qw in atomic parity violation can be interpreted as a measurement of the S parameter. This indicates a new Qw = 72.06 0.44, which is found to be above the standard model pre-... 

An interesting phenomenon observed during the decay measurements was the high relative peak intensity of the short-life 5DX emission in comparison to its emissions under continuous excitation. An analysis of the kinetics of a two-step decay process readily convinces one that this is quite normal. 

Figure 2 - Left IF analysis, using a 100 cm 1 Gaussian filter (solid) (other filter widths gave similar results). The sliding window FFT results are shown for comparison (squares). The inset illustrates the exponential decay of the v7 mode. Right FFT of the IF showing a large peak near 50 cm 1. The resolution of this plot is fundamentally limited by the decay of the v7 mode.

The most conclusive evidence for reaction (16) was recently given by Kohout and Lampe.264 They studied the mercury-sensitized decomposition of H2 and D2 in the presence of a small amount of NO. The products of the reaction were bled through a pinhole into a mass spectrometer for continual analysis. Results are shown in Figure 8-6 for the D2-NO system. They observed mass spectral peaks for DNO, DzO, and N20, but not for (DNO)2. Initially, DNO is produced, but it subsequently decays to form NsO (and D20). The minimum rate constant reported by them for DNO disproportionation was 3.4 x 106 M 1 sec-1. However, more recently Kohout263 in his doctoral dissertation has reported that DaO and N20 are the products of the bimolecular encounter of two DNO molecules. The rate constant is 4.0 x 105 Af-1 sec-1 independent of pressure over the limited pressure range of 30-70 torr. An increase in surface-to-volume ratio of about 50 had no effect on the results. 

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