In Flora Costaricensis, William Burger of the Field Museum in Chicago considered eight of the Piper species that occur in Costa Rica to make up the P. obliquum complex, and six additional species to be closely allied to it (Fig. 9.1; Burger 1971). Piper calcariformis, an additional species assignable to the P. obliquum complex, was later described by Tebbs (1989). Although Burger did not apply ...

Molecular modeling techniques were used to establish relationships between the molecular properties of 45 substituted phenylureas and their octanol/water partition coefficient (log P) and soil sorption normalized to organic carbon (Koc). Log P and Koc values were obtained from the literature. The molecular properties were calculated using MOPAC-MNDO molecular orbital methods. The OSAR models ba...

Ž . Computer-aided molecular design CAMD provides a means for determining molecules or mixtures of Ž . molecules CAMMD having a desirable set of physicochemical properties. The application range of CAMD is restricted due to limitations on the complexity of the generated molecular structures and on the availability of suitable models for property prediction. A new CAMD methodology that addresses...

For three decades, molecular models for water, nature’s most important liquid, have been developed and refined by fitting to structure measured by neutron scattering. The decade-old widely accepted structure of water at room temperature and pressure was recently revised as a byproduct of attempts to understand the structure of high-temperature/high-pressure water for which, in a remarkable reve...

Certain tRNA synthetases have developed highly accurate molecular machinery to discriminate their cognate amino acids. Those aaRSs achieve their goal via editing reaction in the Connective Polypeptide 1 (CP1). Recently mutagenesis studies have revealed the critical importance of residues in the CP1 domain for editing activity and X-ray structures have shown binding mode of noncognate amino acid...

A survey of theoretical studies of charge transfer involving collisions of multiply-charged ions with atomic neutrals (H and He) is presented. The calculations utilized the quantum-mechanical molecular-orbital close-coupling (MOCC) approach where the requisite potential curves and coupling matrix elements have been obtained with the spin-coupled valence bond (SCVB) method. Comparison is made am...

Nonempirical quantum chemical ST0-3G calculations were performed for cluster models of two oxygen-bridged T0 4 tetrahedra (T = Si, Al). The models are based on [(H0)3T0T(0H)3]"structures and, in case of Al-containing models (n = 1,2), their electric neutrality is ensured by adding positive point charges. The calculations suggest the occurrence of X4.I — O —Al^ pairings provided certain electric...

Crystallographic studies play a major role in current efforts towards protein structure determination. However, despite recent advances in computational tools for molecular modeling and graphics, the task of constructing a protein model from crystallographic data remains complex and time-consuming, requiring extensive expert intervention. This paper describes an approach to automating the proce...

Nuclear magnetic resonance (NMR) spectroscopy provides a unique toolbox of experimental probes for studying dynamic processes on a wide range of timescales, ranging from picoseconds to milliseconds and beyond. Along with NMR hardware developments, recent methodological advancements have enabled the characterization of allosteric proteins at unprecedented detail, revealing intriguing aspects of ...

The various methods that comprise the field of molecular modeling are reviewed in the context of their potential for application to the molecular level design of new fire retardants and suppressants. The capabilities of these techniques are demonstrated by performing calculations on systems ranging in molecular complexity from small gas phase molecules to polymers. As a consequence of its funda...