Biomolecules water-soluble

Contact between fluorescent tags on heavily labeled macromolecules generally leads to fluorescence quenching and often precipitation of the labeled antibody.Therefore, it is important not to overlabel the biomolecule. Water-soluble dyes can be used to obtain a high density of... 

The spectra we have so far discussed were recorded using CDC13> the best allround solvent for organic molecules. However, many molecules, especially biomolecules, are only soluble in water biological systems often remain stable only in aqueous solution. Thus NMR measurements in water are extremely important our model compound is also water-soluble, so that we can use it to demonstrate some important experiments. 

To overcome these issues, the water-soluble TCEP was synthesized and successfully used to cleave organic disulfides to sulfhydryls in water (Burns et al., 1991). The advantage of using this phosphine derivative in disulfide reduction as opposed to previous ones is its excellent stability in aqueous solution, its lack of reactivity with other common functionalities in biomolecules, and its freedom from odor. 

As a result of their unique optical and electronic properties, particularly their ability to fluoresce at discrete wavelengths directly proportional to their sizes and material compositions, QDs have found use in many fields, including electronics, biology, medicine, and even cosmetics. The first attempts to modify their surface characteristics to make them water-soluble and biocompatible eventually led to their use as fluorescent labels for biomolecules in many applications (Rogach et al., 1996 Bruchez et al., 1998 Chan and Nie, 1998). 

Water-soluble QDs now are available from a number of manufacturers (Invitrogen, Evident Technologies, and Crystalplex). Each supplier uses their own proprietary methods of surface pacification to create biocompatible particles. Even coated QD clusters are available that contain hundreds of particles bound together in a polymer matrix (Crystalplex). These form intensely bright labels for biomolecules, because the nanocrystals do not quench when clustered together at high density. 

Figure 9.60 Many different thiol-containing linkers can be used to prepare water-soluble QDs. The monothiol compounds suffer from the deficiency of being easily oxidized or displaced off the surface, thus creating holes for potential nonspecific binding. The dithiol linkers are superior in this regard, as they form highly stable dative bonds with the semiconductor metal surface that do not get displaced. The PEG-based linkers are especially effective at creating a biocompatible surface for conjugation with biomolecules.

Click chemistry or Staudinger ligation equipped heterobifunctional crosslinkers containing a hydrophilic PEG spacer provide a stable, yet highly efficient means to conjugate or immobilize biomolecules. The PEG spacer provides water solubility, low nonspecific binding character, and low immunogenicity. 

Figure 18.15 NHS-chromogenic-PEG3-biotin contains an amine-reactive NHS ester that can be used to label biomolecules through an amide linkage. The chromogenic bis-aryl hydrazone group within the spacer arm of the reagent allows the degree of biotinylation to be quantified by measuring its absorbance at 354 nm. The compound also contains a hydrophilic PEG spacer, which provides greater water solubility.

Gee, K.R., Archer, E.A., and Kang, H.C. (1999) 4-Sulfotetrafluorophenyl (STP) esters New water-soluble amine-reactive reagents for labeling biomolecules. Tetrahedron Lett. 40, 1471. 

CeramiSphere technology is not limited to the encapsulation of small water-soluble molecules. It is also used to encapsulate hydrophobic molecules such as essential oils, flavours, vitamins, proteins (including enzymes) and many other biomolecules (such as DNA). 

In principle, there are four basic strategies to compensate for the repulsive effects between the hydrophobic fullerene surface and water (a) encapsulation in the internal hydrophobic moiety of water-soluble hosts like cyclodextrins (Andersson et al., 1992 Murthy and Geckeler, 2001), calixarenes (Kunsagi-Mate et al., 2004) or cyclotriveratrylenes (Rio and Nierengarten, 2002) (b) supramolecular or covalent incorporation of fullerenes or derivatives into water-soluble polymers (Giacalone and Martin, 2006) or biomolecules like proteins (Pellarini et al., 2001 Yang et al., 2007) (c) suspension with the aid of appropriate surfactants and (d) direct exohe-dral functionalization in order to introduce hydrophilic moieties. 

In recent years, several procedures have been developed for handling high molecular weight, water-soluble biomolecules. Several of these procedures are here briefly described. [See the Chapman (1993) and Watson (1985) references for a thorough discussion of these techniques. The Harrison (1992) reference presents a thorough treatment of chemical ionizations.]... 

This technique is widely used on water-soluble biomolecules—proteins, peptides, and carbohydrates in particular. The result is a spectrum whose major peaks consist of the molecular ion with a different number of charges attached. A molecular ion of, for example, about 10,000 Da with a charge (z) of 10 would behave in a mass spectrometer as though its mass were about 1000 daltons. Its mass, therefore, can be determined with a spectrometer of modest resolution—and cost. 

Vitamins and hormones are minor organic biomolecules, but both of them are required by animals for the maintenance of normal growth and health. They differ in that vitamins are not synthesized by animals and must be supplied in diets while hormones are secreted by specialized tissues and carried by the circulatory system to the target cells somewhere in the body to initiate/stimulate specific biochemical or physiological activities. Vitamins (Dyke, 1965) can be classified as water-soluble (B vitamins and vitamin C) or fat-soluble (vitamins A, D, E, and K) and act as cofactors for numerous enzyme catalyzed reactions or cellular processes. Hormones (Nornam and Litwack, 1997) can be classified structurally as follows ... 

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