16) The data in Table I show the fraction of the barrier that is eliminated after partial distortion of CBD from the rectangular minimum toward a square geometry. (17) Maier, G.; Schafer, U.; Sauer, W.; Hartan, H.; Oth, J. F. M. Tetrahedron Lett. 1978, 1837. This explanation has been suggested by Bally, T.;Masamune, S. Tetrahedron 1980,36,343. An alternative explanation is that C-1 and C-3, which are nonequivalent in a rectangular geometry, nevertheless, have nearly identical chemical shifts.(18) It should be noted that the geometry and apparent diamagnetic nature of 3 provide evidence for the correctness of the theoretical prediction of a singlet ground state for CBD, even at a square g e~m e t r y .~~~'~~~'~ (19) Buenker, R. J.; Peyerimhoff, S. D.
Solid
state amide hydrogen/deuterium exchange with mass spectrometric
analysis (ssHDX-MS) was used to assess the conformation of myoglobin
(Mb) in lyophilized formulations, and the results correlated with
the extent of aggregation during storage. Mb was colyophilized with
sucrose (1:1 or 1:8 w/w), mannitol (1:1 w/w), or NaCl (1:1 w/w) or
in the absence of excipients. Immediately after lyophilization, samples
of each formulation were analyzed by ssHDX-MS and Fourier transform
infrared spectroscopy (FTIR) to assess Mb conformation, and by dynamic
light scattering (DLS) and size exclusion chromatography (SEC) to
determine the extent of aggregation. The remaining samples were then
placed on stability at 25 °C and 60% RH or 40 °C and 75%
RH for up to 1 year, withdrawn at intervals, and analyzed for aggregate
content by SEC and DLS. In ssHDX-MS of samples immediately after lyophilization
(t = 0), Mb was less deuterated in solids containing
sucrose (1:1 and 1:8 w/w) than in those containing mannitol (1:1 w/w),
NaCl (1:1 w/w), or Mb alone. Deuterium uptake kinetics and peptide
mass envelopes also indicated greater Mb structural perturbation in
mannitol, NaCl, or Mb-alone samples at t = 0. The
extent of deuterium incorporation and kinetic parameters related to
rapidly and slowly exchanging amide pools (Nfast, Nslow), measured at t = 0, were highly correlated with the extent of aggregation
on storage as measured by SEC. In contrast, the extent of aggregation
was weakly correlated with FTIR band intensity and peak position measured
at t = 0. The results support the use of ssHDX-MS
as a formulation screening tool in developing lyophilized protein
drug products.
We have developed a new system for clinical chemistry analysis, the Vision System, in which centrifugal force is used to separate whole blood, measure reagent and plasma volumes, and complete all steps required for a spectrophotometric analysis. The system is based on use of a multichambered plastic test pack containing liquid reagents, which can be centrifuged at 500 X g in two planes, oriented at right angles to each other. Alternating centrifugal fields allows liquid reagents and plasma to flow into highly precise measuring and mixing chambers. A unique flash lamp and diode array spectrometer provide for optical measurements of 10 test packs at as many as eight wavelengths simultaneously. The temperature of each individual test pack is controlled by using a flash lamp coupled to a liquid crystal temperature sensor. Microprocessor control allows as many as 10 different chemistry reactions to be measured simultaneously on whole-blood, plasma, or serum samples. Comparison with results by an established batch-photometric analyzer demonstrated excellent precision and accuracy for various clinical chemistry tests.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.