The study of the low lying states of linear polyenes is vitally important for the understanding of photobiological processes, including energy transfer in photosynthesis, cistram photoisomerization in visual systems and photosynthetic bacteria, and the photochemistry of vitamin D.le5 The complexity of the naturally occurring polyenes inhibits both computational and experimental investigations o...

case n > 3. In a related field, that of the natural polyenes, the C40-carotenoids, methods have been used in some laboratories2 for the preparation of stereoisomers, viz., reversible isomerization by refiuxing solutions, by iodine or HCl catalysis, and by melting crystals. Irradiation can also be effective. As the adsorption affinity of stereoisomers varies with the configuration, they can be s...

The formation of biexcitons in conjugated polymers is examined within the Pariser-Parr-Pople (PPP) model of polyacetylene. The calculations are done using a scattering formalism that provides a size-consistent description of excited states containing both single and double electron-hole pair excitations. The excited-state absorption spectrum from the 1Bu exciton state was calculated and examine...

OBJECTIVE Candida albicans is the primary causative agent of oral candidosis, and one of its key virulent attributes is considered to be its ability to produce extracellular phospholipases that facilitate cellular invasion. Oral candidosis can be treated with polyenes, and azoles, and the more recently introduced echinocandins. However, once administered, the intraoral concentration of these dr...

We present a formulation of molecular response theory for the description of a quantum mechanical molecular system in the presence of a weak, monochromatic, linearly polarized electromagnetic field without introducing truncated multipolar expansions. The presentation focuses on a description of linear absorption by adopting the energy-loss approach in combination with the complex polarization p...

The cationic cyclization of polyenes has proved to be a useful tool in the synthesis of natural terpenic products.1 During recent years biomimetic approaches using radical chemistry have also been described.2,3 One of the most efficient is based on Mn(III) chemistry, which in the presence of Cu(II) resolves one of the main problems involved in radical reactions, the loss of funcionality.4,5 Ano...

The incidence of disseminated candidiasis has increased dramatically over the past several decades. Fortunately, in recent years, a variety of new antifungal agents have become available to treat these infections. On the basis of efficacy, safety, and cost considerations, fluconazole is the agent of choice for the empirical treatment of disseminated candidiasis in nonneutropenic, hemodynamicall...

The J-OC-PSP (decomposition of J into Orbital Contributions using Orbital Currents and Partial Spin Polarization) method is applied to analyze NMR spin-spin coupling constants in polyenes, which were calculated using coupled perturbed density functional theory in connection with the B3LYP hybrid functional and a [7s,6p,2d/4s,2p] basis set. The analysis revealed that the pi-mechanism for Fermi c...