Integrals hydrogen bonds

Li ME, Yamato K, Ferguson JS, Gong B. Sequence-specific association in aqueous media by integrating hydrogen bonding and dynamic covalent interactions. J Am Chem Soc 2006 128 12628-12629. 

The two strands which make up DNA are held together by hydrogen bonds between complementary pairs of bases adenine paired with thymine and guanine paired with cytosine. The integrity of the genetic code (and of life as we know it) depends on error-free transmission of base-pairing information. 

Fig. 35.—(a) Stereo view of about a turn of the 3-fold double helix of potassium gellan (41). The two chains are drawn in open and filled bonds for distinction. Both intra- and inter-chain hydrogen bonds stabilize the helix. The vertical line is the helix axis. Octahedrally coordinated potassium ions (crossed circles) and triply hydrogen-bonded water molecules (open circles) located above the ions are integral components of the structure of 41. 

The integrity of the hydrogen-bonding network remains intact. 

In series with a desolvation energy barrier required to disrupt aqueous solute hydrogen bonds [14], the lipid bilayer offers a practically impermeable barrier to hydrophilic solutes. It follows that significant transepithelial transport of water-soluble molecules must be conducted paracellularly or mediated by solute translocation via specific integral membrane proteins (Fig. 6). Transcellular permeability of lipophilic solutes depends on their solubility in GI membrane lipids relative to their aqueous solubility. This lumped parameter, membrane permeability,... 

The structure of the major trimeric LHCII complex has been recently obtained at 2.72 A (Figure 7.3) (Liu et al., 2004). It was revealed that each 25kDa protein monomer contains three transmembrane and three amphiphilic a-helixes. In addition, each monomer binds 14 chlorophyll (8 Chi a and 6 Chi b) and 4 xanthophyll molecules 1 neoxanthin, 2 luteins, and 1 violaxanthin. The first three xanthophylls are situated close to the integral helixes and are tightly bound to some amino acids by hydrogen bonds to hydroxyl oxygen atoms and van der Waals interactions to chlorophylls, and hydrophobic amino acids such as tryptophan and phenylalanine. 

---