Ethane-1,2-diyl bis­(benzene­dithio­ate)

In the crystal structure, the title compound, C16H14S4, is located on an inversion center and exhibits a gauche+–trans–gauche− conformation in the S—CH2—CH2—S bond sequence. The S—C=S plane makes a dihedral angle of 30.63 (17)° with the phenyl ring. An inter­molecular C—H⋯π inter­action is observed

RBCS1A and RBCS3B, two major members within the Arabidopsis RBCS multigene family, function to yield sufficient Rubisco content for leaf photosynthetic capacity

Ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) small subunit (RBCS) is encoded by a nuclear RBCS multigene family in many plant species. The contribution of the RBCS multigenes to accumulation of Rubisco holoenzyme and photosynthetic characteristics remains unclear. T-DNA insertion mutants of RBCS1A (rbcs1a-1) and RBCS3B (rbcs3b-1) were isolated among the four Arabidopsis RBCS genes, and a double mutant (rbcs1a3b-1) was generated. RBCS1A mRNA was not detected in rbcs1a-1 and rbcs1a3b-1, while the RBCS3B mRNA level was suppressed to ∼20% of the wild-type level in rbcs3b-1 and rbcs1a3b-1 leaves. As a result, total RBCS mRNA levels declined to 52, 79, and 23% of the wild-type level in rbcs1a-1, rbcs3b-1, and rbcs1a3b-1, respectively. Rubisco contents showed declines similar to total RBCS mRNA levels, and the ratio of Rubisco-nitrogen to total nitrogen was 62, 78, and 40% of the wild-type level in rbcs1a-1, rbcs3b-1, and rbcs1a3b-1, respectively. The effects of RBCS1A and RBCS3B mutations in rbcs1a3b-1 were clearly additive. The rates of CO2 assimilation at ambient CO2 of 40 Pa were reduced with decreased Rubisco contents in the respective mutant leaves. Although the RBCS composition in the Rubisco holoenzyme changed, the CO2 assimilation rates per unit of Rubisco content were the same irrespective of the genotype. These results clearly indicate that RBCS1A and RBCS3B contribute to accumulation of Rubisco in Arabidopsis leaves and that these genes work additively to yield sufficient Rubisco for photosynthetic capacity. It is also suggested that the RBCS composition in the Rubisco holoenzyme does not affect photosynthesis under the present ambient [CO2] conditions

Conformational and orientational characteristics of chain molecules placed in a nematic field : n-decane and 1,6-dimethoxyhexane dissolved in 4′'-methoxybenzylidene-4-n-butylaniline (MBBA)

Conformational and orientational characteristics of n-decane (n-C$_{10}$) and 1,6-dimethoxyhexane (1,6-DMH) chains dissolved in a liquid crystal 4$'$-methoxybenzylidene-4-n-butylaniline (MBBA) have been investigated. The two chain molecules, although having the same number of skeletal bonds, are known to take quite different configurations in the isotropic state. The phase behavior of the MBBA + 1,6-DMH system was observed ; the initial slopes $\beta_{\rm N}^{\infty}$ and $\beta_{\rm I}^{\infty}$ of the phase boundaries, representing the ability of the solute to disturb the nematic order, were determined, and compared with those of the MBBA + n-C$_{10}$ system. The thermodynamic data show that, in the nematic environment, the n-C$_{10}$ molecules is more rigid and extended than 1,6-DMH. Deuterium NMR spectra of partially deuterated MBBA incorporated in the solutions were measured, and the orientational order parameters of the solvent were evaluated. Using the Photinos-Samulski-Toriumi (P-S-T) model and the single-ordering-matrix (SOM) model, $^{2}$H-NMR quadrupolar splittings and D-D dipolar couplings observed for the perdeuterated solutes were analyzed. The results obtained by the P-S-T model indicate that, even in the nematic phase, the n-C$_{10}$ molecule is very flexible as in the isotropic phase. On the other hand, the SOM analysis gave a consequence that the n-C$_{10}$ chain possesses considerable rigidity. Thus, it can be concluded that the SOM model rather than the P-S-T model afforded results consistent with the thermodynamic data. For 1,6-DMH, the P-S-T simulation did not satisfactorily reproduce the D-D dipolar couplings observed, while the SOM scheme achieved the good agreement between the calculations and observations in all the examples. According to the SOM analysis, the 1,6-DMH molecule, keeping its inherent conformational preference, conforms itself to the nematic field by taking anisotropic configurations such as kink ($g^{\pm}~tg^{\mp}$), crankshaft ($g^{\pm}~tg^{\pm}$) and jog ($g^{\pm}~tttg^{\mp}$ arrangements

Conformational and Orientational Characteristics of Chain Molecules Placed in Nematic Fields. Part II

Deuterium NMR quadrupolar splittings and $^2$H – $^2$H dipolar couplings observed from perdeuterated 1,6-dimethoxyhexane (CD$_3$O(CD$_2$)$_6$OCD$_3$) dissolved in a liquid crystal 4$'$-methoxybenzylidene-4-$n$-butylaniline (MBBA) were analyzed using the single-ordering-matrix (SOM) and the Photinos-Samulski-Toriumi (P-S-T) models. Within the framework of the rotational isomeric state approximation, intramolecular interactions up to the third-order (between atoms and groups separated by five bonds) were considered. The geometrical parameters and intramolecular interaction energies determined from ab initio molecular orbital calculations were employed. The two simulation models yielded fair agreement between theory and experiment, but were found to give quite different images of the solute chain: (the SOM model), the solute becomes rigid and extended to conform itself to the nematic field; (the P-S-T model), the solute has almost the same degree of flexibility as in the free state, but populations of the anisotropic conformers are selectively enhanced. To reveal the true conformational characteristics of chain molecules in nematic fields, experimental techniques to enable direct and quantitative measurements of the bond conformations are necessary

Butane-1,4-diyl bis(benzenecarbodithioate)

The title compound, C18H18S4, which lies on an inversion center, adopts a trans–gauche+–trans–gauche−–trans (tg+tg−t) conformation of the S—CH2—CH2—CH2—CH2—S bond sequence. In the crystal, a π–π interaction with a centroid–centroid distance of 3.8797 (16) Å is observed

N,N′-(Ethane-1,2-diyl)dibenzenecarbothioamide

The title compound, C16H16N2S2, adopts a gauche+–gauche+–gauche+ (g+g+g+) conformation in the NH—CH2—CH2—NH bond sequence. In the crystal, molecules are connected by pairs of N—H...S=C hydrogen bonds and C—H...π interactions, forming a tape structure along the c-axis direction

Structure–Property Relationships of Poly(ethylene carbonate) and Poly(propylene carbonate)

Conformational characteristics of poly­(ethylene carbonate) (PEC) and poly­(propylene carbonate) (PPC) have been revealed via molecular orbital (MO) calculations and nuclear magnetic resonance (NMR) experiments on model compounds with the same bond sequences as those of the polycarbonates. Bond conformations derived from the MO calculations on the models were in exact agreement with those from the NMR experiments. Both PEC and PPC were indicated to adopt distorted conformations including a number of gauche bonds and cover themselves with negative charges, thus failing to form a regular packing and remaining amorphous. The MO data were applied to the refined rotational isomeric state (RIS) calculations to yield configurational properties such as the characteristic ratio, its temperature coefficient, the configurational entropy, and average geometrical parameters of unperturbed PEC and PPC chains. In the RIS calculations on PPC, the regio- and stereosequences were generated according to the Bernoulli trial or Markov stochastic process. In consequence, it was shown that the configurational properties of PPC do not depend significantly on its regio- and stereoregularities. The internal energy contribution to rubberlike chain elasticity, calculated from the temperature coefficient of the characteristic ratio, has indicated the possibility that PEC and PPC will behave as elastomers. The practical applications and potential utilizations of the polycarbonates are discussed on the basis of the conformational characteristics and configurational properties

N,N′-(Propane-1,3-diyl)dibenzothioamide

The title compound, C17H18N2S2, exhibits a trans–trans–trans–gauche+ (tttg+) conformation with regard to the NH–CH2–CH2–CH2–NH bond sequence. In the crystal, molecules are connected by N—H...S=C and C—H...S=C hydrogen bonds, forming a herringbone arrangement along the c-axis direction. The two thioamide groups make dihedral angles of 43.0 (2) and 33.1 (2)° with the adjacent phenyl rings