Hydrogen bonding, between

Moderate errors in the total pressure calculations occur for the systems chloroform-ethanol-n-heptane and chloroform-acetone-methanol. Here strong hydrogen bonding between chloroform and alcohol creates unusual deviations from ideality for both alcohol-chloroform systems, the activity coefficients show... 

The properties of water are seen to differ greatly from the other hydrides the deviations can be largely explained by the formation of hydrogen bonds between water molecules. 

The simulation (Lu et al., 1998) suggested how Ig domains achieve their chief design requirement of bursting one by one when subjected to external forces. At small extensions, the hydrogen bonds between strands A and B and between strands A and G prevent significant extension of a domain, i.e.. 

Proteins are biopolymers formed by one or more continuous chains of covalently linked amino acids. Hydrogen bonds between non-adjacent amino acids stabilize the so-called elements of secondary structure, a-helices and / —sheets. A number of secondary structure elements then assemble to form a compact unit with a specific fold, a so-called domain. Experience has shown that a number of folds seem to be preferred, maybe because they are especially suited to perform biological protein function. A complete protein may consist of one or more domains. 

Fig. 7.23 In simulations of stearic add on a hydrophobic surface hydrogen bonding between the head groups is important in controlling the orientation of the molecules [Kim et al, 1994b],...

If one would ask a chemist not burdened with any knowledge about the peculiar thermodynamics that characterise hydrophobic hydration, what would happen upon transfer of a nonpolar molecule from the gas phase to water, he or she would probably predict that this process is entropy driven and enthalpically highly unfavourable. This opinion, he or she wo ild support with the suggestion that in order to create room for the nonpolar solute in the aqueous solution, hydrogen bonds between water molecules would have to be sacrificed. 

Solubility in Water A familiar physical property of alkanes is contained m the adage oil and water don t mix Alkanes—indeed all hydrocarbons—are virtually insoluble m water In order for a hydrocarbon to dissolve m water the framework of hydrogen bonds between water molecules would become more ordered m the region around each mole cule of the dissolved hydrocarbon This increase m order which corresponds to a decrease m entropy signals a process that can be favorable only if it is reasonably... 

Hydrogen bonds between —OH groups are stronger than those between —NH groups as a comparison of the boiling points of water (H2O 100 C) and ammonia (NH3 —33 C) demonstrates... 

Intramolecular hydrogen bond between the —OH group and the carbonyl oxygen... 

FIGURE 19 2 Attrac tions between regions of positive (blue) and negative (red) electrostatic potential are responsible for intermo lecular hydrogen bonding between two molecules of acetic acid... 

Section 27 19 Two secondary structures of proteins are particularly prominent The pleated sheet is stabilized by hydrogen bonds between N—H and C=0 groups of adjacent chains The a helix is stabilized by hydrogen bonds within a single polypeptide chain... 

In addition to hydrogen bonding between the two polynucleotide chains the double helical arrangement is stabilized by having its negatively charged phosphate groups on the outside where they are m contact with water and various cations Na" Mg and ammonium ions for example Attractive van der Waals forces between the... 

C which causes the strands to separate by breaking the hydrogen bonds between them [Figure 28 14(Zi)]... 

V Hel IX (Section 27 19) One type of protein secondary struc ture It IS a right handed helix characterized by hydrogen bonds between NH and C=0 groups It contains approxi mately 3 6 amino acids per turn... 

Liquids that are sufficiently volatile to be treated as gases (as in GC) are usually not very polar and have little or no hydrogen bonding between molecules. As molecular mass increases and as polar and hydrogen-bonding forces increase, it becomes increasingly difficult to treat a sample as a liquid with inlet systems such as El and chemical ionization (Cl), which require the sample to be in vapor form. Therefore, there is a transition from volatile to nonvolatile liquids, and different inlet systems may be needed. At this point, LC begins to become important for sample preparation and connection to a mass spectrometer. 

The various mechanical properties of polyamides may be traced in many instances to the possibility of intermolecular hydrogen bonding between the polymer molecules and to the relatively stiff chains these substances possess. The latter, in turn, may be understood by considering still another equilibrium, this one among resonance structures along the chain backbone ... 

Figure 6.14 Hydrogen bonding between phenol and diethylether...

Fig. 3. (a) Chemical stmcture of a synthetic cycHc peptide composed of an alternating sequence of D- and L-amino acids. The side chains of the amino acids have been chosen such that the peripheral functional groups of the dat rings are hydrophobic and allow insertion into Hpid bilayers, (b) Proposed stmcture of a self-assembled transmembrane pore comprised of hydrogen bonded cycHc peptides. The channel is stabilized by hydrogen bonds between the peptide backbones of the individual molecules. These synthetic pores have been demonstrated to form ion channels in Hpid bilayers (71). 

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