Why Threonine Is an Essential Amino Acid in Mammals and Birds: Studies at the Enzyme Level.

The only pathway for the synthesis of essential amino acids in vertebrates is reversible transamination of their keto analogs with glutamic acid. At the same time, it is commonly accepted that such essential amino acids as lysine and threonine are not involved in transamination and, therefore, cannot be synthesized from their keto analogs. However, using radiolabeled isotopes, synthesis of threonine was demonstrated in rat liver and in a reaction mixture containing chicken liver threonine dehydrogenase.

Reason for Indispensability of Threonine in Humans and Other Mammals in Comparative Aspect.

The essential amino acid threonine is not synthesized in vertebrates, so it must be obtained from food. During evolution, the decomposition of threonine has changed. Because the decomposition of threonine catalyzed by threonine dehydratase is irreversible, in the present work attention is focused on threonine dehydrogenase to show the inability of this enzyme to synthesize threonine in a reaction that would be the reverse of the reaction of threonine decomposition.

A novel feature of intramolecular vibrational redistribution in propargyl alcohol and propargyl amine.

Intramolecular vibrational redistribution (IVR) from the terminal acetylene mode nu(HC) has been studied for four molecules: H-C[Triple Bond]C-CH(3) (propyne), H-C[Triple Bond]C-CH(2)Cl (propargyl chloride), H-C[Triple Bond]C-CH(2)OH (propargyl alcohol), and H-C[Triple Bond]C-CH(2)NH(2) (propargyl amine). The experiments were performed with the room-temperature gases. The transition mid R:0-->mid R:1 in the mode nu(HC) was pumped by a short laser pulse.

Cavity ringdown spectroscopic detection of nitric oxide with a continuous-wave quantum-cascade laser.

A spectroscopic gas sensor for nitric oxide (NO) detection based on a cavity ringdown technique was designed and evaluated. A cw quantum-cascade distributed-feedback laser operating at 5.2 mum was used as a tunable single-frequency light source.