Steric effects

About: Steric effects is a research topic. Over the lifetime, 16112 publications have been published within this topic receiving 319615 citations. The topic is also known as: steric hindrance.

PEG-epirubicin Conjugates with High Drug Loading

Abstract: PEG is used as a polymeric carrier for low molecular weight drugs, but limitations arise from the fact that only one or two hydroxyl residues are on each polymer. Therefore, the synthesis of dendrimeric structures, based on amino adipic acid or beta-glutamic acid, as a branching molecule, built on a PEG diol of Mw 10,000Da was investigated. The large polycyclic drug epirubicin molecule was chosen as a model to investigate the influence of structure branching and drug steric hindrance during coupling reactions. Several derivatives with increased numbers of drug molecules linked to each PEG chain were synthesized and their physical, chemical and biological properties were studied. The use of specific amino bicarboxylic acids (amino adipic acid or -glutamic acid), as the branching moiety for the dendrimer synthesis, allowed linking the hindered molecule epirubicin to multibranched PEG. Most drug loaded conjugates only dissolve in water following dissolution in DMSO. This solubility problem was solved by addi...

Theoretical Calculation of Hydrogen-Bonding Strength for Drug Molecules

Abstract: Hydrogen bond is an important type of interaction between drug molecules and their receptors. We present here a computational method for accurately predicting the hydrogen-bonding strength for different acceptors with respect to a given donor or vice versa. The method is based on quantum chemistry DFT calculation of the interaction energy between hydrogen bond donors and acceptors. An excellent linear correlation is observed between the calculated hydrogen-bonding energies and the experimentally measured hydrogen-bonding constants log Kβ on a variety of known hydrogen bond acceptors and donors. These results not only indicate the predictive power of this method but also shed light on factors that determine the magnitude of experimentally measured hydrogen-bonding constants for different acceptors with respect to a given donor, suggesting a primarily enthalpic contribution from hydrogen-bonding energy. The method can be used for evaluating the effects of steric interference and inhibitor binding geometry on hydrogen-bonding strength in drug design.

New Phenyl-Substituted PPV Derivatives for Polymer Light-emitting Diodes−Synthesis, Characterization and Structure−Property Relationship Study

Abstract: Three new PPV derivatives with dialkoxyphenyl substituents, BEH2P−PPV, BEH3P−PPV, and BEH4P−PPV have been synthesized. The polymers were characterized by FT-IR, 1H NMR, and elemental analysis. The polymers possess excellent solubility, high molecular weights, high photoluminescence efficiencies and good thermal stability. The influence of substitution pattern on the formation of structural defects has been investigated by measuring the signal due to tolane−bisbenzyl moieties (TBB) in the proton NMR spectra. BEH2P−PPV with a steric phenyl group at the ortho-position on the side phenyl ring shows the lowest amount of TBB, which indicates suitable steric hindrance can be applied to suppress the formation of irregular head-to-head and tail-to-tail linkage in the polymer chains. In addition, the polarity of solvents used for the Gilch polymerization will also affect the amount of irregular structure in the polymers. Polar solvents such as THF will result in polymers with low TBB content. Energy level measureme...