Molecular hydrophobic

Certain of these peptoid antibiotics are also selective for bacterial, rather than mammalian, cells. The selectivity of these peptoids has been measured in terms of their capacity to cause hemolysis of human erythrocytes at or near their MIC (Tab. 1.3). Interestingly, the amount of hemolysis induced by these peptoids correlates well with their hydrophobicity as there is an increasing extent of hemolysis as molecular hydrophobicity increases. These results suggest that highly hydro-phobic compounds of this class are poorly selective antibiotics. The most active antibacterial peptoids, T2-15 and T3-12, have quite low hemolytic activity near their MICs. Although highly antibacterial in vitro, T3-17 is also very hemolytic at its MIC value. 

A from the center of a positive ionizable group was identified. However, its predictive performance on a test set consisted of eight structurally similar compounds was relatively poor. To achieve a computational model with greater predictability, a descriptor-based QSPR model was also developed. Descriptors related to molecular hydrophobicity as well as hydrogen bond donor, shape and charge features contributed to explain hOCTl inhibitor properties of the analyzed compounds. 

The hydrophobicity of some monoazoic dyes was determined by RP-TLC. The chemical structure of analytes are depicted in Fig. 3.1. RP-TLC plates were prepared by impregnating silica plates for 24 h in a hexane-paraffin oil (90 10, v/v) mixture. Mobile phases consisted of methanol-0.5 M HC1 mixed in various volume ratios. Methanol concentration varied between 30-60 per cent in steps of 6 and 3 per cent. The RM value characterizing molecular hydrophobicity was calculated by... 

Liu et al. [27] introduced a new lipoaffinity descriptor to account for the effect of molecular hydrophobicity on BBB penetration. The descriptor was defined based on Kier and Hall s atom-type electrotopological state indices and therefore its evaluation is fast, requires no molecular 3D information, and... 

Larger molecular size and hydrophibcity reduces the permeation rate, whereas bpoaffinity (molecular hydrophobicity) enhances the BBB permeability of the molecules. 

Molecular hydrophobicity (or lipophilicity) is perhaps one of the most often studied physicochemical properties, particularly in organic and medicinal chemistry. It is most frequently expressed via the partition- (P) or distribution (D) coefficients, which represent the ratio of concentrations of a given compound in the two phases of a... 

In an aqueous medium these wtermolecular attractive interactions make a strong contribution to biopolymer self-association and inclusion complex formation, as well as to the flocculation of biopolymer-coated colloidal particles. // //Y/molecular hydrophobic interactions commonly influence the level of folding/unfolding of macromolecules as well as their detailed conformations. 

Another recent trend is to show the importance of hydrophobic profiles rather than molecular hydrophobicity. Giuliani et al. (2002) suggested nonlinear signal analysis methods in the elucidation of protein sequence-structure relationships. The major algorithm used for analyzing hydrophobicity sequences or profiles was recurrence quantification analysis (RQA), in which a recurrence plot depicted a single trajectory as a two-dimensional representation of experimental time-series data. Examples of the global properties used in this... 

CONTENTS Preface, C. Allen Bush. Thermodynamic Solvent Isotope Effects and Molecular Hydrophobicity, Terrence G. Oas and Eric J. Toone. Membrane Interactions of Hemolytic and Antibacterial Peptides, Karl Lohner and Richard M. Epand. Spin-Labeled Metabolite Analogs as Probes of Enzyme Structure, Chakravarthy Narasimhan and Henry M. Miziorko. Current Perspectives on the Mechanism of Catalysis by the Enzyme Enolase, John M. Brewer and Lukasz Leb-ioda. Protein-DNA Interactions The Papillomavirus E2 Proteins as a Model System, Rashmi S. Hedge. NMR-Based Structure Determination for Unlabeled RNA and DNA, Philip N. Borer, Lucia Pappalardo, Deborah J. Kenwood, and Istvan Pelczer. Evolution of Mononuclear to Binuclear CuA An EPR Study, William E. Antholine. Index. 

Oas, T.G. Toone, E.J. (1997) Thermodynamic solvent isotope effects and molecular hydrophobicity,... 

Without doubt log Kow has been the most commonly utilized physicochemical descriptor in QSAR analysis. The reason is that it is considered to represent molecular hydrophobicity (it is incorrect, however, to consider a log Kow value as hydrophobicity — it merely describes it). Hydrophobicity is an extremely important property in predictive toxicology. As described in Chapter 1 hydrophobicity is assumed to account for the capability to enter, pass through, and/or accumulate in cell membranes, as well as a being one of the main forces in binding effects. Therefore hydrophobicity, as described by log K v, is a major driving force in predicting toxicity (Chapters 8 and 12) and distribution in humans (Chapter 11) and the environment (Chapters 14 to 16). 

Horinek, D. et al. Molecular hydrophobic attraction and ion-specific effects studied by molecular dynamics. Langmuir 2008, 24, 1271-1283. 

The experimental results [7] show that the surface pressure is positive and increases with alcohol concentration. This indicates that the alcohol accumulates at the water air interface. Furthermore, the surface pressure increases with increase in the alkyl chain length at constant bulk concentration, demonstrating that the extent to which the alcohol accumulates at the interface depends on the alkyl chain length, or molecular hydrophobicity. 

In summary, it is more likely that two different effects are called hydrophobic interaction (1) the known molecular hydrophobic effect, - which could bring about a relatively short-range attractive surface force,and (2) formation of capillary bridges-cavities between two hydro-phobic surfaces. For now, there is sufficient evidence showing that both effects exist in reality, often in interplay with each other. 

The antineoplastic activity of six native cyclic hexapeptides(RA-I, II, III, IV, V, and VII) and seven related compounds were also examined against P388 lymphocytic leukemia in mice (Fig. 20). The mice received 10 mg/kg/ day (except for RA-VII and RA-III 4.0 and 2.0 mg/kg/day) for 5 consecutive days. The results were as follows. The small differences of antitumor activity among these compounds could be explained to some extent by the molecular hydrophobicities, as previously mentioned, but a remarkable decrease in antitumor activity was observed in the RA-IV compounds A, A-diAc, E, E-Me, and E-Ac, whose a-proton at the Cj3-position of Tyr-6 was replaced with bulky substituent groups. In spite of a similar replacement at C)8, the activity of compounds B and C did not decrease. From these findings, it may be concluded that the introduction of large substituent groups at the a-side of the RA series results in decreased antitumor activity. This seems to play an important role in the mechanism of antitumor activity. The antitumor activity decrease of RA-II could be explained from the viewpoint of the molecular hydrophobicity rather than from the a-block hypothesis. 

GREENBERG Odor Intensity and Molecular Hydrophobic Properties 179... 

Davis, J. G., K. P. Gierszal, P. Wang, and D. Ben-Amotz, Water structural transformation at molecular hydrophobic interfaces. Nature, 2012. 49 582-585. 

Figure 17 displays a spherical water drop rolling off a glass slide coated with a rough AI2O3 layer plus a molecular hydrophobic top layer. The drop removes artificial contaminants (graphite powder) on its track. 

Poly(methyl acrylate)-grafted silica (Sil-MA, ) showed unexpectedly unique selectivity in a reversed phase mode. The unusual nature of Sil-MA is emphasized by Fig. 2. Octadecylated silica shows a good linearity in the log -log P plots (Fig. 2a), indicating that the elution order is understandable by molecular hydrophobicity of solutes. On the other hand, Sil-MA provides no similar result. As shown in Fig. 2b, it seems to show that Sil-MA , instead, recognizes the molecular size (i.e., the number of the... 

Similar specificities in HPLC have been realized with poly(4-vinylpyridine) and poly(acrylonitrile). The similarity of these polymers can be characterized by the fact that their residual groups include locally polarized moieties with vr-electrons. Here, their uniqueness is summarized through the results of poly(4-vinylpyridine)-grafted silica (Sil-VP ) Sil-VP is less sensitive for molecular hydrophobicity of solutes, as shown in a typical chromatogram of Fig. 4A. This is proof of a great difference from ordinary ODS. On the contrary, higher retention and selectivity (Fig. 4C) are observed for PAHs or tt-electron-containing substances, especially sensitive for difference of the molecular planarities of solutes... 

Hydrophobicity, from the Greek hydro (water) and (phobia) aversion, is a term referring to the way a molecule likes or does not like water. A compound with a high hydrophobicity will not be water soluble. It is apolar. Conversely, a compound with low hydrophobicity is said to be hydrophilic or polar. It is likely to be water soluble. In between the two extremes, hydrophobicity varies. A scale is needed. The problem is that hydrophobicity, or the polarity of a compound, depends on several parameters such as the dipole moment, the dielectric constant, the polarizability, the proton donor or acceptor character, or even the boiling point to molecular mass ratio. Since the end of the nineteenth century, the octanol-water partition coefficient, which should preferably be termed distribution constant, Po/w> has been used with success as a measure of molecular hydrophobicity. The log Pq/w is a convenient scale. Compounds with a positive log Pq/w value are more and more hydrophobic or apolar as the value increases. Compounds with a negative log Pq/w value are hydrophilic or polar. ... 

The Revalue is the fundamental parameter in planar chromatography to describe the position of a spot on a developed chromatogram. values in linear, circular, and anticircular chromatography were defined. Correlations between these types of R were evidenced for conversion of linear R values in circular and anticircular and unidimensional multiple development. Definition of thermodynamic and relative Revalues were also reported and discussed. In addition, the importance of Rm value, which has a linear relationship with structural elements of the solute and can be used to characterize molecular hydrophobicity in reversed planar chromatography, was evidenced. 

In addition Rm value can be used to characterize molecular hydrophobicity in reversed-phase planar chromatography by elution with water-organic solvent mixtures according to the Soczewinski-Wachtmeister equation ... 

As discussed in the section Single-anchor grafting, in high-density ODA prepared by the grafting-from method, a main interaction source for molecular recognition is derived from a carbonyl-77 moiety and not from molecular hydrophobicity. Fig. 7 shows the correlation between log k and log P for Sil-gf-ODA, Sil-ODA , and polymeric ODS... 

Cis- and fra/i -stilbenes as geometrical isomers are good candidates for the evaluation of molecular-shape selectivity in HPLC. They have the same carbon number per molecule, and, thus, their molecular hydrophobicities are similar but the molecular planarities are absolutely different. The selectivity at is 1.33, 2.41, and 4.32 for ODS-p, Sil-ODA , and Sil-gf-ODA , respectively, clearly indicating higher selectivity by ODA -grafted silica prepared by grafting-from method however. 

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