Of l,3-dihydroxy-2-propanone

AH,B units at opposite ends of the molecule, just as in the case of l,3-dihydroxy-2-propanone (see Section II,3,a,ii), so that the molecule cannot align itself correctly on the receptor surface.Odorant molecules have been observed to behave similarly. The poor polarization of the taste receptor is enhanced by the combined effect of (a) the absence of a ring-oxygen atom, and hence a polar center, and (b) the presence of hydrophobic, methylene groups. 

The rate of the reaction of l,3-dihydroxy-2-propanone with o-phenylenediamine is much lower than with glycolaldehyde and oL-glyceralde-hyde. The time-dependence of the reaction of oL-glyceraldehyde with o-phenylenediamine in water is shown in Fig. 7. The cathodic waves are... 

The distribution of branched- versus normal-chain species may be a consequence of the base-catalyzed Lobry de Bruyn-Alberda van Eken-stein equilibrium between aldose and ketose. For example, in the addition of formaldehyde to a mixture of glyceraldehyde and l,3-dihydroxy-2-propanone, the relative proportion of l,3-dihydroxy-2-propanone to... 

An interesting compound having a structure analogous to that of d-fructopyranose is l,3-dihydroxy-2-propanone ( dihydroxyacetone, 24) ... 

The isolation of uridine 5 -(l,3-dihydroxy-2-propanone pyrophosphate) from a Pneumococcus strain has been reported.202... 

Possibly not found because of the small quantities used. "Also identified l,3-dihydroxy-2-propanone, DL-glucose, DL-fructose, DL-mannose, DL-arabinose, DL-lyxose, and DL-xylose (and, possibly, DL-ribose). 

The almost exclusive formation of 4(5)-(hydroxymethyl)imidazole (27) from D-fructose, l,3-dihydroxy-2-propanone, and D-fructose-containing compounds (for example, sucrose) is to be expected... 

These conclusions are borne out by the data on some phosphorylated ketoses83 that cannot form pyranoses or furanoses. 5,6-Dideoxy-D-fhreo-hexulose 1-phosphate (1) contains 96% (by i.r.) or 91% (by n.m.r.) of the keto form, and D-en/fhro-pentulose 1,5-bisphosphate (2) contains 84% (by i.r.) or 88% (by n.m.r. spectroscopy80 ) in aqueous solution in the hydrates, there would be 1,3-parallel interactions. There are no such interactions in the hydrate of l,5-dihydroxy-2-pentanone 1,5-bisphosphate (3), but here one of the carbon atoms vicinal to the carbonyl group carries no hydroxyl group, and there is 84% of the keto form in equilibrium. l,3-Dihydroxy-2-propanone phosphate has two neighboring hydroxyl groups and no 1,3-parallel interactions only 55% is in the keto form and 45% is present as the hydrate.83,84... 

In the limited sense that this reaction may be viewed as an attack by a nucleophilic species on an aldehyde, it resembles the chemical aldol condensation and the enzymic aldolase condensation. Recent studies of the latter reaction have demonstrated the formation of a l,3-dihydroxy-2-propanone phosphate-aldolase complex, capable of exchanging a carbon-... 

Related to the interpretation of the effects of radiation on nucleic acids are the studies on the formation of labile phosphate esters in solutions of simple phosphates by irradiation. When glyceritol 1- and 2-phosphates are irradiated with 200 KV x-rays, inorganic phosphate is liberated. The former gives l,3-dihydroxy-2-propanone phosphate, and the latter, an acid-labile phosphate ester. " Detailed studies on methyl, ethyl, propyl, butyl, and amyl phosphates have indicated the mode of formation of such labile phosphate esters. Two reactions have been recognized ... 

Evidence has also been educed for the formation of two constituents, re-ductone and l,3-dihydroxy-2-propanone, by symmetrical scission of the D-fructose molecule these constituents are mainly responsible for the peak at 285-290 m/u in the ultraviolet absorption spectrum of the D-fructose solutions. 

Some of the l,3-dihydroxy-2-propanone phosphate (see Fig. 4) may be reduced to glycerol 3-phosphate, which is then hydrolyzed by a specific phosphatase to glycerol, and this is eliminated from the cells.243 Certain yeasts are notorious for producing acid Saccharomyces bailii (Zygosaccharomyces acidifaciens)... 

A dehydration of this type has actually been observed as a side reaction of a Lobry de Bruyn-Alberda van Ekenstein transformation in a very simple system. Thus, in experiments with the DL-glycerose-l,3-dihy-droxy-2-propanone isomerization in acetate, formate, and trimethylacetate buffers, pyruvaldehyde appeared in the reaction mixtures. (The formation of pyruvaldehyde from l,3-dihydroxy-2-propanone- and dl-glycerose-mineral acid mixtures had been observed much earlier.) Since these experiments in acidic buffers established that this reaction is subject to general acid and base catalysis, pyruvaldehyde must be formed in alkaline mixtures also. The results of Wohl s and Evans and Hass s experiments with DL-glycerose in alkaline solutions containing phenyl-hydrazine, in which pyruvaldehyde phenylosazone was isolated, support this view. 

Nearly all of the investigations of the kinetics of Lobry de Bruyn-Alberda van Ekenstein reactions have failed because of the complications imposed by side-reactions. It has only recently been found that good kinetic data can be obtained for the DL-glycerose-l,3-dihydroxy-2-propanone interconversion. This Section mainly concerns the work with this simple system, which contains implications for the mechanisms of all Lobry de Bruyn-Alberda van Ekenstein reactions, and the attempts to extend it to the higher sugars. 

The DL-glycerose-l,3-dihydroxy-2-propanone isomerization was found to proceed at measurable rates at 50° in acidic buffers. Moreover, under these conditions, the irreversible dehydration to pyruvaldehyde appeared to be the only side-reaction of any consequence. It was actually fortunate that pyruvaldehyde formation occurred, since this permitted examination of the isomerization and dehydration reactions within a single system. 

An estimate of the equilibrium constant for UL-glycerose-l, 3-dihydroxy-2-propanone interconversion was also made in this investigation by start-... 

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