Tritium incorporation

In the polystyrenes produced by cationic initiators most of the chain-ends are terminal indanyl groups, and olefinic groups are rare. As this terminal indanyl group cannot be aluminated like a double bond, the amount of tritium incorporated comes only from the initial AlBr2CH2CHPh-groups and the few residual terminal double bonds and it, therefore, represents (approximately) the total number of initiated chains. 

The oxidation of530 with the ozone adduct 531 is carried out at —78 °C, giving the oxaphosphetane 532. Then, tritiated ethanol is added and the reaction mixture heated to room temperature. The rate of tritium incorporation thus obtained is very high 262) (for an explanation of the mechanism see Chapter 2). 

For preparative deuterium or tritium labelling, organomagnesium compounds are less generally used than organolithium compounds, but similar considerations should apply [5], In the following example a remarkably high degree of tritium incorporation was achieved [6] ... 

Three types of radiation-induced procedures have been used including (a) recoil tritiation, (b) Wilzbach gas irradiation7 with its modifications, and (c) radiation synthesis.8 All these methods utilize high-energy ionizing radiation to achieve tritium incorporation. Wilzbach exchange7 is the most satisfactory of the three and has been the most widely used. Radiation synthesis is a relatively recent development of limited but valuable specificity. 

Halogen substitution in the 5-position of the pyrimidines leads to very little tritium incorporation whereas activity at the mCi/mM level... 

Despite the paucity of data for orientation studies with substituted heterocyclics labeled by the Wilzbach method, extensive work has been done with analogous aromatic compounds and, thus, by extrapolation, a number of general predictions can be made for heterocyclic systems. For example, in toluene34 tritium incorporation in the ring predominates over side-chain labeling. 

The reactivities differ for ortho, meta, and para positions of toluene. In anthranilic acid (10), positions 3 and 5 in the molecule possess 49.8 and 27.4% of the total activity thus, tritium incorporation tends to be highest at positions of highest electron density.35 In isopropanol,35 the hydroxyl group incorporates approximately three times as much isotope as any other hydrogen position, while tritiation of the secondary C-H is slightly more efficient than the primary C-H. In the aliphatic esters of aromatic carboxylic acids, the aryl hydrogens tritiate ten times faster than alkyl hydrogens.10,36... 

Samples of the same batch were tested for the absence of any cytotoxic contaminations in a highly sensitive in vitro test [81]. The recombinant proteins were added to EBV-transformed cytotoxic T cells in a concentration range from 0.001 to 10 [xg/ml. No change in viability or tritium incorporation was seen in the treated cells. In contrast, cells treated under the same conditions with the toxic allergen Asp f 1 were effectively killed. We conclude that our preparation of Alt a 1 is nontoxic. Based on this and on earlier observations with other allergens purified using the same method, Alt a 1 and Altemaria enolase (see below) were approved by the local ethics committee for clinical testing. 

Lanthanide shift reagents have been used to determine the site of deuterium ° or tritium incorporation in compounds by H, or H NMR spectroscopy. This includes deuteriation of hexopyranosides analyzed by H NMR , the low level incorporation of... 

Saljoughian, M. and Williams, P.G., Recent developments in tritium incorporation for radiotracer studies, Curr. Pharm. Des., 6(10), 1029, 2000. 

---