The collective vibrational modes of dihydropyridine in nifedipine studied by terahertz spectroscopy.

Cardiovascular pharmaceuticals have drawn huge attention in drug development. Nifedipine (NFD) is an important member of calcium channel blockers (CCB) with the structural characteristic of dihydropyridine (DHP), but the binding mechanism to its target remains an open question. Even though several analytical techniques have been used for structural characterizations, the information of collective vibrational behavior is still lacking. In this work, we use terahertz (THz) spectroscopy to investigate the spectral fingerprints of NFD, and quantitatively evaluate the temperature-induced frequency shifts. Combined with quantum chemical calculations, each THz fingerprint is attributed to specific collective vibrational modes. The collective vibrations of DHP are mainly distributed below 2.5 THz, which provides complementary information to understand the behavior of rigid DHP ring. The rotation of methyl group and the wagging of nitrophenyl group are widely distributed in the range of 1.0-4.0 THz, which is helpful for the conformational recognition between NFD and target molecule. THz spectroscopy is demonstrated to be suitable for characterizing the collective vibrational modes of DHP and elucidating the drug-target binding behavior from the perspective of noncovalent interactions. It has the potential to become a non-invasive technology for conformational analysis and pharmaceutical development.

A novel rice gene, NRR responds to macronutrient deficiency and regulates root growth.

To better understand the response of rice to nutrient stress, we have taken a systematic approach to identify rice genes that respond to deficiency of macronutrients and affect rice growth. We report here the expression and biological functions of a previously uncharacterized rice gene that we have named NRR (nutrition response and root growth). NRR is alternatively spliced, producing two 5'-coterminal transcripts, NRRa and NRRb, encoding two proteins of 308 and 223 aa, respectively. Compared to NRRb, NRRa possesses an additional CCT domain at the C-terminus. Expression of NRR in rice seedling roots was significantly influenced by deficiency of macronutrients. Knock-down of expression of NRRa or NRRb by RNA interference resulted in enhanced rice root growth. By contrast, overexpression of NRRa in rice exhibited significantly retarded root growth. These results revealed that both NRRa and NRRb played negative regulatory roles in rice root growth. Our findings suggest that NRRa and NRRb, acting as the key components, modulate the rice root architecture with the availability of macronutrients.