Spacer aliphatic

Local Anaesthetics. Figure 1 Common structure of local anaesthetics. A lipophilic moiety on the left, an aliphatic spacer containing an ester or amide bond in the middle and an amine group on the right are the typical structural elements for local anaesthetic drugs. 

A dispersant that can be used in drilling fluids, spacer fluids, cement slurries, completion fluids, and mixtures of drilling fluids and cement slurries controls the rheologic properties of and enhances the filtrate control in these fluids. The dispersant consists of polymers derived from monomeric residues, including low-molecular-weight olefins that may be sulfonated or phosphonated, unsaturated dicarboxylic acids, ethylenically unsaturated anhydrides, unsaturated aliphatic monocarboxylic acids, vinyl alcohols and diols, and sulfonated or phosphonated styrene. The sulfonic acid, phosphonic acid, and carboxylic acid groups on the polymers may be present in neutralized form as alkali metal or ammonium salts [192,193]. 

Following the convergent procedure, dendrimers of type 58,59 and 60 have been prepared from the chiral core triol 54 and achiral Frechet-type [62] ben-zylic branch bromides. In the series of dendrimers with aromatic spacers (60) and without spacers (58), the optical activity [a]D decreased on going from the 1st (not shown in Fig. 21) to the 2nd generation, whereas with aliphatic spacers... 

Using the same versatile modular synthetic strategy, the same group developed biotinylated bi- (438) and tetra-antennary (439) mannosylated glycoconjugates to capture and detect E. coli cells, and compared the relative capturing ability of these molecules to commercial polyclonal antibodies (Fig. 47).318 Instead of aliphatic spacers, tetraethylene glycol linkers were used to diminish nonspecific binding and to impart flexibility for a better fit in the active sites. 

Although NHS-LC-biotin and sulfo-NHS-LC-biotin are very popular reagents for biotinylation, they both result in hydrophobic aliphatic biotin modifications on proteins and antibodies. Unfortunately, these groups have a tendency to aggregate in aqueous solution and may cause protein precipitation or loss of activity over time. For this reason, the use of more hydrophilic PEG-based biotin compounds of approximately the same spacer length may be a better alternative for maintaining water solubility of modified proteins (Chapter 18). 

Perhaps a better design for a bis-hydrazide compound to modify carboxylate particles would include a short PEG spacer arm between the two hydrazide groups. This type of linker would result in a hydrophilic surface due to the presence of the PEG spacers, while providing the terminal hydrazide functionality necessary for coupling to carbonyl compounds. Unfortunately, this type of compound is not currently available, so the aliphatic bis-hydrazides are the only choice. 

Immobilized cryptates. Like the crowns, cryptates have been immobilized on polymeric backbones. A typical system is given by (221) (Cinquini, Colonna, Molinari, Montanari Tundo, 1976). In this case, the polymeric matrix is polystyrene cross-linked with p-divinyl benzene and the cage is connected to this matrix via a long-chain aliphatic spacer group. This reagent is quite effective as a (triphase) transfer catalyst. 

The two aliphatic amino acids have also been replaced by the hydrophobic spacers 3-(aminomethyl)benzoic acid (3-AMBA see 9, Fig. 2) [28] and 3- and 4-aminobenzoic acid (3- and 4-ABA) as well as 2-phenylaminobenzoic acid (see 10, Fig. 2) [29,30]. These compounds displayed IC50 values in the nanomolar range, and 10 (R = H) blocked the growth in nude mice of a human lung carcinoma expressing oncogenic Ras [31]. 

Figure 5.5 Architecture of a layered SAM consisting of a rigid biphenyl unit (BP) on top of an aliphatic spacer chain of m methylene units. The surface-terminating tail group can be either chemically inert (e.g., X = CH3, H) or active (e.g., X = CN).

In some cases, it is desirable to add a spacer which elongates the stopcock molecule so that the length of the tail can be controlled. This can be a tool to improve the solubility of the whole molecule. Polar groups might help to bind the molecules more strongly inside of the zeolite channels. Spacers which are sufficiently flexible so that they can bend the tail into the zeolite channels include, for example, aliphatic chains, polyethers, or amides. 

In the crystal structures, the inhibitors coordinate to the active site zinc and make a series of hydrogen bonds via their hydroxamic acid moiety. The hydroxamic acids are linked by a flexible spacer with bulky cap groups. The aromatic or aliphatic spacer participates in van der Waals interactions throughout the long charmel, whereas the terminal part of the inhibitor interacts with residues at the rim of HDAC. In general, the binding mode of the cocrystallized inhibitors TSA and SAHA is conserved among the different species and subtypes [35]. 

---