Evidence for multiple states

R. W. Harrigan, G. D. Hager, and G. A. Crosby, Evidence for multiple-state emission from ruthenium(II) complexes, Chem. Phys. Lett. 21, 487-490(1973). 

In a detailed study of the equilibria involved in the urea transition, Tanford (354) showed that a two-state process could not explain the RNase data and that the cooperative units, whose unfolding was reflected in the measurements, must be much less than the total molecule. Each unit was probably not more than one-third of the total molecule. This conclusion was based on Tanford s theory and the data of Nelson and Hummel (351) and of Foss and Schellman (355). The midpoint of the transition at room temperature in 0.1 M KC1 and neutral pH is about 6 M urea. Barnard (356) found a midpoint at 6.7 M urea at pH 7 and 25°C. By fluorescence the midpoint was about 6.5 M urea (308). Between 12 and 16 molecules of urea per molecule of protein appeared to be involved in the transition (356), 12 being the kinetic order of the unfolding reaction and 16 being the value derived from the slope of the equilibrium curve. Again evidence for multiple states was presented. 

Evidence for Multiple States of Adsorbed.Proteins. The evidence to be reviewed here supporting the existence of multiple states of adsorbed proteins derives from many types of studies (see Table III). In each study, different techniques were used to study the behavior of proteins at interfaces but none was specifically designed nor applied to investigate the possible existence of multiple states of adsorbed proteins. Furthermore, the proteins, surfaces, and objectives of each study varied. Nonetheless, this diverse data base is consistent in support of the existence of multiple states, and its diversity may therefore actually provide greater... 

In conclusion we may state that there is evidence for multiple ion-pair recombination in spurs yet a theoretical analysis of free-ion yield and scavenging at low-LET based on the geminate ion-pair picture is meaningful in view of the similarity of the recombination process in the geminate and multiple ion-pair cases. However, if this analogy holds, the geminate ionization yield has to be somewhat less than the true ionization yield. 

Perez, D. M., Hwa, J., Gaivin, R., Mathur, M., Brown, F., and Graham, R. M. (1996). Constitutive activation of a single effector pathway Evidence for multiple activation states of a G protein-coupled receptor. Mol Pharmacol. 49, 112-122. 

Kasai and McLeod (26) have measured the ESR spectrum of Cu atoms in krypton and have shown that there is no evidence for multiple trapping sites and that the Cu atoms reside in an octahedral site. For Cu atoms in an octahedral site, spin orbit interaction splits the state into 1/2 components. 

Subbayya, I., and Balaram, H. (2000). Evidence for multiple active states of Plasmodium falciparum hypoxanthine-guanine-xanthine phosphoribosyltransferase. Biochem. Biophys. Res. Commun. 279,433-437. 

Sepunaru L, Friedman N, Pecht I, Sheves M, Cahen D (2012) Temperature-dependent solid-state electron transport through bacteriorhodopsin experimental evidence for multiple transport paths through proteins. J Am Chem Soc. doi 10.1021/ Ja2097139... 

Chapter 33, by Haddad, presents evidence for multiple oxygen sensors in the central neurons, which participate in acute as well as chronic responses to hypoxia in a variety of species including Drosophila and mammals. He states that acute responses to oxygen deprivation involve K efflux and Na influx, whereas chronic responses involve protein alteration in plasma membrane, cytosol, and mitochondria. The effects of hypoxia on central neurons described by Haddad are reminiscent of that described in the carotid body. Haddad concludes that there are multiple oxygen sensors in the central nervous system. 

The electrostatically favored cation (Li) and anion (RE) arrangement implies the presence of two different E-, Si- and Li sorts, which has been established by solution and solid-state NMR spectroscopy. The electronic structures of the mixed-valent pnictides 10 and 11 have been simply described as electron-deficient clusters with delocalized framework electrons. Formally the latter consist of two low-valent anediyl moieties RE and eight andiides (RE)2- (E = P, As). The relatively large E-E distances of >4 A exclude the occurrence of localized E-E bonds. However, delocalization of the cluster valence electrons is achieved without Li-Li bonds via Li-mediated multiple bonding. Evidence for this has been seen in the NMR spectra (31P, 7Li, 29Si), which are in accordance with the electron delocalization model (see later discussion). 

The phase transitions for 90 were also evident in the UV-VIS spectra, as seen in Figure 26 M has an absorption maximum at 315 nm, QM at 350 nm, and multiple absorptions with peaks at ca. 315, 350, 365, and 378 nm are evident for phase I and the other phases. Isosbestic points observed between the phases indicate coexistence of two states during structural evolution, and the existence of multiple UV peaks for a phase is considered to indicate the existence of several conformations for that phase. In this report, 0 all structures were modeled with conformations between all-T and all-D thus, the conformational nature of the different phases of (Si-/z-Dec2U is not clear. Similar UV absorptions observed for structurally related polymers, such as PDHS (see below), are suggestive of comparable backbone conformations. 

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