Hydrophilic calculation

Lipophilic and hydrophilic calculations are performed at -0.6 and -3.0kcalmol", respectively. Critical packing is a good parameter to predict molecular packing such as in micelle formation, and may be relevant in solubility studies in which the melting point plays an important role. 

Based on the calculation of the solvatation free energy of methylene fragment with carboxyl at the aliphatic carboxylic acids extraction, the uniqueness of cloud-point phases was demonstrated, manifested in their ability to energetically profitably extract both hydrophilic and hydrophobic molecules of substrates. The conclusion is made about the universality of this phenomenon and its applicability to other kinds of organized media on the surfactant base. 

One of the most important characteristics of the emulsifier is its CMC, which is defined as the critical concentration value below which no micelle formation occurs. The critical micelle concentration of an emulsifier is determined by the structure and the number of hydrophilic and hydrophobic groups included in the emulsifier molecule. The hydrophile-lipophile balance (HLB) number is a good criterion for the selection of proper emulsifier. The HLB scale was developed by W. C. Griffin [46,47]. Based on his approach, the HLB number of an emulsifier can be calculated by dividing... 

The dried polyoxazoline-modified silica gel was immersed into distilled water. The adsorption property of the resulting gel was estimated by the water content. The water uptake was calculated from an expression of (W -W)jW, where Wis the weight of dried gel and W is the weight of water-absorbed gel. The modified gel showed a higher water-adsorption property than that of untreated silica gel, which absorbed 10.8 multiples of water. The water uptake of modified gel was up to 13.7 multiples of the weight of dried gel. Thus, silica gel has been made more hydrophilic by a polyoxazoline segment. 

Figure 9. Theoretical C,E curves (1, 2, 3) for single-crystal faces and (4) for a model polycrystalline surface calculated by the superposition of the C,E curves at E= const [Eq. (49)] with = 02 = = 1/3 1. (a) Faces with strong hydrophilicity and (b, c) faces with...

Parsons-Zobel plots have been constructed for all the systems at a = 0 in the range 0.02 < c < 0.2 M. These plots were linear, with the value of the slope very close to unity. The values of C, obtained by extrapolation of the C-1, C plots to C a = 0 were in good agreement with those calculated from the C,E curves for the 0.1 M NaC104 + DMF system according to the GCSG model.358 The value of Q increases in the sequence of electrodes Hg < Tl(Ga) < In(Ga) < Ga as the hydrophilicity of the electrode surface rises. 

Good agreement between C(- and the dipole moment of the solvent (H20) molecules (i.e., by the hydrophilicity of metals) established by Trasatti25,31 was found and the reasons for this phenomenon were explained 428 The Valette and Hamelin data150 251 387-391 are in agreement with the data from quantum-chemical calculations of water adsorption at metal clusters 436-439 where for fee metals it was found that the electrode-H20 interaction increases as the interfacial density of atoms decreases. 

On the whole, theoretical calculations provide only a general insight into the problem of water-metal interactions, probably because not all factors are appropriately taken into account. Thus the agreement of AX data with A

theoretical calculations. Nevertheless, each author claims good agreement with some experimental facts, with the outcome that plenty of hydrophilicity scales have been suggested23,153,352 389 399 834 870 890,892 893 based on different parameters these have increased the entropy of the situation with a loss of clarity. 

Upper panel The hydropathy profile of the entire 69 kD precursor protein is shown. The abscissa is amino acid residues and the ordinate, positive values indicate hydrophilic. The black and hatched rectangles at the bottom of the figure denote the calculated signal sequence and amino-terminal propeptide domains, respectively. The mature and carboxyl-terminal domains are labeled. N-linked core glycosylation consensus sites are depicted by branched structures. 

The combination of hydrophilic and hydrophobic parts of a molecule defines its amphiphilicity. A program has been described to calculate this property and calibrated against experimental values obtained from surface activity measurements [133]. These values can possibly be used to predict effect on membranes leading to cytotoxicity or phospholipidosis, but may also contain information, not yet unraveled, on permeability. Surface activity measurements have also been used to make eshmates of oral absorphon [126]. 

One of the first but yet successful and weU known method, MLOGP, was developed by Moriguchi et al. [64]. MLOGP uses the sum of Hpophilic (carbons and halogens) and hydrophilic atoms (nitrogens and oxygens) as two basic descriptors. These two descriptors were able to explain 73% of the variance in the experimental log P values for 1230 compounds. The use of 11 correction factors covered 91% of the variance. Due to the simplicity of implementation, the MLOGP method was widely used as a calculation and reference approach for many years. 

In almost all theoretical studies of AGf , it is postulated or tacitly understood that when an ion is transferred across the 0/W interface, it strips off solvated molecules completely, and hence the crystal ionic radius is usually employed for the calculation of AGfr°. Although Abraham and Liszi [17], in considering the transfer between mutually saturated solvents, were aware of the effects of hydration of ions in organic solvents in which water is quite soluble (e.g., 1-octanol, 1-pentanol, and methylisobutyl ketone), they concluded that in solvents such as NB andl,2-DCE, the solubility of water is rather small and most ions in the water-saturated solvent exist as unhydrated entities. However, even a water-immiscible organic solvent such as NB dissolves a considerable amount of water (e.g., ca. 170mM H2O in NB). In such a medium, hydrophilic ions such as Li, Na, Ca, Ba, CH, and Br are selectively solvated by water. This phenomenon has become apparent since at least 1968 by solvent extraction studies with the Karl-Fischer method [35 5]. Rais et al. [35] and Iwachido and coworkers [36-39] determined hydration numbers, i.e., the number of coextracted water molecules, for alkali and alkaline earth metal... 

With respect to the size and charge selectivity of paracellular pathways, equivalent pore theory has been utilized to calculate an effective radius based on the membrane transport of uncharged hydrophilic molecules, while equivalent circuit theory has been used to separate mediated from paracellular membrane transport of small ions. The term equivalent should be emphasized, as selectivity parameters are obtained from membrane transport data, so phenomenological information is used to quantitate the magnitude of aqueous pathways... 

The HLB of a relatively pure poly(oxyethylene) adduct can be calculated from theoretical data [37]. For these agents the HLB is an indication of percentage by mass of the hydrophilic portion, divided by five to give a conveniently small number. For example, if the hydrophilic portion of a purely hypothetical nonionic agent accounted for 100% of the molecule (such a product cannot, of course, exist), its HLB is 20. Similarly, a more plausible product in which 85% of the molecule is accounted for by the hydrophilic portion has an HLB of 85/5 = 17. The ICI Americas Inc. method of calculating the theoretical HLB of a sorbitan monolaurate nonionic having 20 oxyethylene units per molecule is given in... 

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