Racemization dating definition

12 May

The change from a pure enantiomer to a racemate can change its density, melting point, solubility, heat of fusion, refractive index, and in various spectra.

Crystalization of a racemate can result in separate ( ) and (-) forms, or a single racemic compound.

Its implementation is based on analysing how often the term «racemization» appears in digitalised printed sources in English between the year 1500 and the present day.

2.8 Racemization During Peptide Synthesis One of the most serious problems encountered in early peptide synthesis was partial racemization of the incorporated amino acids. NH2 NH2 Scheme 13.3 Racemization of (R)-phenylethylamine with base at high temperature.

Again, those like Goodfriend and Hare (1995) have pointed out the "difficulties in estimating the amount of asparagine in proteins and reminded researchers of the dangers of extrapolating from the behaviour of pure Asn in solution at high temperature, to the behaviour of Asn in proteins associated with biominerals at ambient temperature . The rate of racemization can not be standardized by itself because it is too changeable.

Thus, because of the rate problem, this dating technique must rely on other dating techniques to standardize its findings.

The translations of racemization from English to other languages presented in this section have been obtained through automatic statistical translation; where the essential translation unit is the word «racemization» in English.

The graph expresses the annual evolution of the frequency of use of the word «racemization» during the past 500 years.

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Racemization occurs when one pure form of an enantiomer is converted into equal proportion of both enantiomers, forming a racemate.

These two forms are called "enantiomers", "chirals", or "stereoisomers", which basically means that they have the same molecular and structural formula but cannot be superimposed on each other no matter how they are oriented in space.

Such extrapolations have been fairly recently (1999) called into question by experiments showing that models based on high temperature kinetics fail to predict racemization kinetics at physiologic temperatures (i.e., 37 C). We argue that the D: L ratio of Asx reflects the proportion of non-helical to helical collagen "The local buffering effects of bone and shell matrixes are supposed to limit this effect, but it is still something to consider as potentially significant when acting over the course of tens of thousands to millions of years.replacement of the asparagine residue with aspartic acid resulted in a 34-fold decrease in the rate of succinimide (Asu) formation.

1 Racemization of (S)-9 using 1 mole of various bases. v) Racemization was very rapid in the presence of alkoxides. indicated 0.85% racemization when triethylammonium salts were used, but no racemization with tetrabutylammonium salts.

A catalytic amount of potassium tert-butoxide (as low as 5 mol-%) was sufficient for ... The four-component condensation method has been used in the preparation of a cyclic eledoisin analogue and ...