Molecular structure and puckering potential of gas-phase 1-pyrroline as determined by microwave and infrared spectroscopy

The microwave spectrum of 1-pyrroline has been measured from 8 to 48 GHz. The transitions have been assigned to those of the ground state and the four lowest excited states of the ring-puckering vibration of monomer, which is a five-membered ring molecule with one CN double bond. The trimer, which exists in the liquid phase, has not been detected in the gas phase. The geometrical structure of the monomer has been estimated by an ab initio calculation and the trimer by a molecular mechanics calculation. The former is consistent with the experimental rotational constants. A gas-phase infrared spectrum has also been measured, and the ring-puckering potential has been determined by an analysis of the combination bands of the ring-puckering mode and the ring-stretching modes. The potential is described using a puckering coordinate, z, as V(z) = az² + bz⁴, where $\text{a = ?3.358(16) × 10}{}^4\text{cm}{}^{\mathrm{?1}}\text{A}\text{?}{}^{\mathrm{?2}}$ and $\text{b = 1.345(9) × 10}{}^6\text{cm}{}^{\mathrm{?1}}\text{A}\text{?}{}^{\mathrm{?4}}$; these values are intermediate of the corresponding values for cyclopentene and 1-pyrazoline. The nuclear quadrupole coupling constants, χ_aa = ?4.39(10), χ_bb = 1.04(10), and χ_cc = 3.35(10) MHz, have been determined by an analysis of well-resolved hyperfine splittings. These constants have been reproduced by an ab initio calculation with a 4-31G(N¹) basis set.     

DNA DAMAGE and ITS REPAIR IN Dictyostelium discoideum IRRADIATED BY HEALTH LAMP LIGHT (UV- B)

Irradiation by health lamp (HL) light (280–320 nm) more efficiently induced cell killing and mutation in a radiation sensitive mutant (TW8) of Dictyostelium discoideum as compared with the parental wild-type strain (NC4). This light as well as a germicidal lamp-light (254 nm) produced pyrimidine dimers. The dimers were removed from DNA molecules by excision repair in NC4, but more slowly in TW8. It is suggested that pyrimidine dimers are the main DNA damage caused by HL light in D. discoideum , and that this results in cell killing and induced mutation.     

Structural and magnetic properties of the phase transition in absorbed and non-absorbed copper(II) trans-1,4-cyclohexanedicarboxylate

A large amount of toluene can be absorbed into the 1-dimensional tunnels in copper(II) trans-1,4-cyclohexane dicarboxylate (Cu(trans-1,4-OOCC₆H₁₀C)) at room temperature, and it can be desorbed by evacuation at elevated temperatures. The reversible absorption/desorption behavior of toluene was studied by magnetic susceptibility measurements using SQUID magnetometer and by powder X-ray diffractometry with high-energy synchrotron radiation at SPring-8, Japan. The first order phase transition was observed at 160 K in the magnetic susceptibility curve for the empty (non-absorbed or desorbed) sample, and the structural difference between the low and high temperature phases was detected in the powder X-ray diffraction patterns. On the other hand, no phase transition was observed in fully toluene-absorbed sample, and the structure was similar to that of the low temperature phase of the empty sample. The absorption/desorption behavior observed in the present study coincides with the results of heat capacity measurements by adiabatic calorimetry reported previously.