Ligating

Plenary 7 7. P M Champion et al, e-mail address champ neu.edu (TRRRS). Femtosecond impulsive preparation and timing of ground and excited state Raman coherences in heme proteins. Discovery of coherence transfer along a de-ligation coordinate. See above for fiirther connnent. 

Crystal stmctures of Grignard reagents do not necessarily correspond to their stmcture in solution. In general, the crystal stmctures (61—64) indicate the reagents are ligated with THF or diethyl ether and are frequentiy observed to be dimers. The Mg atoms in the dimers do not have a Mg—Mg bond instead the dimers are typically held together by a haUde bridge. 

Fig. 10. The receptor—G-protein sequence. An activated receptor interacts with the trimeric GDP-ligated receptor to cause an interchange of GDP by GTP and dissociation into the activated Ga—GTP (left) and G y (right) subunits. These then interact with a variety of effectors. The purpose of the activated...

Fig. 4. Steps in making a cDNA library. Cellular mRNA is used as a template to make a complementary DNA. This cDNA is then ligated to a plasmid,...

The automated method differs from the ICSH method chiefly in that oxidation and ligation of heme iron occur after the hemes have been released from globin. Therefore, ferricyanide and cyanide need not diffuse into the hemoglobin and methemoglobin, respectively. Because diffusion is rate-limiting in this reaction sequence, the overall reaction time is reduced from approximately three minutes for the manual method to 3 —15 seconds for the automated method. Reaction sequences in the Coulter S + II and the Technicon H 1 and H 2 are similar. Moreover, similar reactions are used in the other Coulter systems and in the TOA and Unipath instmments. 

Affinity Chromatography. This technique involves the use of a bioselective stationary phase placed in contact with the material to be purified, the ligate. Because of its rather selective interaction, sometimes called a lock-and-key mechanism, this method is more selective than other lc systems based on differential solubiHty. Affinity chromatography is sometimes called bioselective adsorption. 

Gouaux, J.E., Lipscomb, W.N. Crystal structures of phosphonoacetamide ligated T and phosphono-acetamide and malonate ligated R states of aspartate carbamoyltransferase at 2.8 A resolution and neutral pH. Biochemistry 29 389-402, 1990. 

FIGURE 13.4 Blunt-end ligation using phage T4 DNA ligase, which catalyzes the ATP-dependent ligation of DNA molecules. AMP and PP are by-products. 

It is clear that some boranes are amphoteric Lewis acid/bases — that is they can act either as electron-pair donors as above or as electron-pair acceptors (e.g. in L.BH3 and L.B1H7). It follows that a borane donor could conceivably ligate... 

---