Puzzle observations

Further experiments with labeled precursors were necessary to shed a little more light on this puzzling observation. Pyramine, biosynthesized from AIRs labeled with, 4C on C-l on the ribose part, exhibited only marginal radioactivity. This result rules out C-l of ribose in AIRs as a precursor of pyramine. This conclusion was confirmed with a precursor labeled at the C-l position with the stable l3C isotope. The mass spectrum of the ethylthio derivative of pyramine was identical with that of an unlabeled sample (Scheme 9). 

It had been established by midcentury that W-al koxycarbonylam ino acids do not isomerize during coupling. However, there emerged the puzzling observation that... 

A puzzling observation in the above mentioned investigation of the effect of positive supercoiling on nucleosome structure [51] was that the number of nucleosomes... 

One puzzling observation is the formation of large quantities of benzoic acid in all three solvents. The authors suggest that since only a trace of oxygen can be present during irradiation, it must be formed from some unstable product which decomposes during work up. 

A second puzzling observation was the inverse dependence of hydrosilation rates on the concentration of substrate. In a rate study in which the concentration of acetophenone was varied, rate suppression was observed as [acetophenone] increased. Since raising [acetophenone] is expected to shift the equilibrium for adduct formation towards the adduct, this phenomenon argues against direct involvement of the adduct in the catalytic cycle for hydrosilation. Finally, it was observed that, in a competition experiment between benzaldehyde and ethylbenzoate, benzaldehyde was hydrosilated almost exclusively at a comparable rate to the non-competitive hydrosilation of the aldehyde. This observation shows that the relative basicity of the substrate does play an important role in the reaction, determining the chemoselectivity of the reaction. 

Due to a number of puzzling observations one might ask whether the iron sites in the two protomers of R2 are identical. The purified protein from E. coli normally contains lnl.2 Tyr and ca 3 Fe per R2 as opposed to the expected integer values of 2 and 4, respectively. The crystal structure indicates at least 70n80% occupancy at the iron sites. In a recent publica-... 

The equilibria 8.13 of the cobalt-containing species explain a puzzling observation The addition of base turns the effects of CO pressure (or total pressure at constant synthesis-gas ratio) and phosphine concentration on rate into their opposites In the absence of base, an increase in CO pressure or decrease in phosphine... 

The situation may be summarized as follows Most likely, thrombosthenin is the effector of clot retraction activity there remain, however, a series of puzzling observations, which still await explanation. Until then, clot retraction is still as good a playground for speculation as it has been for the past 100 years. 

I became deeply interested in chemistry soon after I came to Berkeley. Just the general atmosphere of the college was conducive to this chemistry was in the air. When members of the faculty would meet, let s say in the halls, the discussion would be about some seminar topic that hadn t been quite resolved or about a puzzling observation that someone had made, sometimes in the freshman laboratory. What got to me early was not only their enthusiasm for the subject but their frankness in admitting the limits of their understanding and their willingness to learn from each other. There was little pretense, and they didn t feel that they had to impress others. At any rate, the fire was lit there quite early in my stay. 

A puzzling observation has recently been made by R. A. Jahnke and D. B. Jahnke (in press). They found that in sediments above the saturation depth that contain high concentrations of calcium carbonate, the ratio of the calcium carbonate dissolution rate to the organic matter remineralization rate was substantially less than at other types of sites. They have suggested that this may be the result of exchange on carbonate particle surfaces coupled with particle mixing, but this process has yet to be clearly substantiated. 

Teflon was not discovered as a result of a planned series of experiments designed to produce this chemical compound. Rather, it was discovered when a scientist made a simple but puzzling observation. 

A puzzling observation that led to the discovery of isotopes was the fact that lead obtained from uranium-containing ores had an atomic mass lower by two full atomic mass units than lead obtained from thorium-containing ores. Explain this result, using the fact that decay of radioactive uranium and thorium to stable lead occurs via alpha and beta emission. 

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