Hydrophobicity fragment

Rekker, R. E. The Hydrophobic Fragmental Constant Its Derivation and Application with a Means of Characterizing Membrane Systems, Elsevier, Amsterdam, 1977. 

Mannhold, R., Rekker, R. F. The hydrophobic fragmental constant approach for calculating log P in octanol/ water and aliphatic hydrocarbon/water systems. Perspect. Drug Discov. Des. 2000, 18,1-18. 

Nys, G. G., Rekker, R. F. Statistical analysis of a series of partition coefficients with special reference to the predictability of folding of drug molecules. Introduction of hydrophobic fragmental constants (/-values). Chim. Therap. 1973, 8, 521-535. 

Rekker, R. F., Mannhold, R. Calculation of Drug Lipophilicity. The Hydrophobic Fragmental Constant Approach, VCH, Weinheim, 1992. 

Mannhold, R., Rekker, R. F., Dross, K., Bijloo, G., De Vries, G. The lipophilic behaviour of organic compounds 1. An updating of the hydrophobic fragmental... 

Methods that deduce a pharmacophore, an arrangement in 3D space of features that contribute or detract from binding and look for its presence in the database that is searched. This method places emphasis on features like hydrogen bond donors, hydrogen bond acceptors, acidic or basic units and hydrophobic fragments and opens the possibility of identifying unexpected scaffolds with required features (pharmacophore-based VS or PHBVS). 

Various methods by which the Kow of PAHs could be calculated are based on their molecular structures, i. e., a quantitative structure-property relationship (QSPR) approach [ 1,199,200]. One of the most famous techniques involves summation of hydrophobic fragmental constants (or f-values) for all groups in a molecule of a specific compound. On the other hand, Aboul-Kassim [1] and Aboul-Kassim et al. [202, 203] introduced a modeling technique based on the molecular connectivity indices of various PAHs, ranging from low- to high-molecular weight compounds. More details are given in Chap. 4 of this volume. 

Rekker RF (1977) The hydrophobic fragmental constant. Elsevier, Amsterdam/New York, NY, 220 pp... 

The measurement of the solubility of drugs in polar and non-polar media is very important in the pharmaceutical field. One method proposed to describe this solubility is the partition coefficient between octanol and water. The mathematical calculation of an octanol-water partition coefficient from values for functional groups was first proposed by Hansch et al. as Hansch s n constants,1 and was later developed by Rekker as hydrophobic fragmental constants (logP).2 This method was further improved by the use of molecular connectivities.17 The prediction of logP values can be performed by either a computer program or by manual calculation. For example, approximate partition coefficients (log P) have been calculated by Rekker s method ... 

The difference between the log k values measured and those predicted by Equations 6.1 and 6.2 from log P values calculated by Rekker s hydrophobic fragmental constant was within 5%. An example of logk values obtained experimentally compared with those predicted from Rekker s logP values is shown in Figure 6.2, where the predicted and measured retention factors of aromatic acids are shown. The correlation coefficient was 0.993 (n = 32), and the slope was 1.014. The precision is very high. 

A second interesting class of amphiphilic polymers is the polysoaps or miceUar polymers as they are often referred to. Such polymers are composed of hydrophilic and hydrophobic fragments leading to various molecular architectures that have been discussed in detail by A. Laschewsky [78]. The precise structure of the resulting micelles, that is, whether they are intra- or intermolecular assembhes, is still subject to discussion because the polymer structure is so versatile. Possible micellar structures are depicted in Fig. 6.8. The most interesting feature of such polymers with respect to their application in catalysis is (i) their remarkable abil-... 

R. F. Rekker (1977). The Hydrophobic Fragmental Constant. New York Elsevier. 

R. R. Rekker, "The Hydrophobic Fragmental Constant, Pharmacochemistry Library, Vol. 1, Elsevier, New York, 19TT-... 

Fig. 1. Schematic representation of molecular structures used for the photoseparation of charges, (a) Molecular monolayers on the base of fatty acids (b) lipid bilayers (c) lipid vesicles (d) micelles (e) microemulsions. The circles and ellipses stand for polar fragments the elongated rectangles, the wavy and straight lines depict hydrophobic fragments. Examples of substances forming the depicted structures are given in Fig. 3.

Rekker, R. F. 1977The Hydrophobic Fragmental ConstahtewYork Elsevier. 

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