Frozen thawing

Figure 7. Survival of frozen-thawed mouse marrow stem cells based on colonyforming activity) as a function of the concentration of glycerol in the tyrode saline suspending medium. (From Leibo et al., 1970.)...

Figure 10. Survival (% unhemolyzed cells) of frozen-thawed human red blood cells as a function of the concentration of glycerol in the medium (buffered saline) and as a function of temperature. Freezing was slow (1.7 °C/min) thawing was rapid. (From Mazur, 1977b, based on data of Souzu and Mazur, 1978.)...

Mazur, P., Miller, R.H., Leibo, S.P. (1974). Survival of frozen-thawed bovine red cells as a function of the permeation of glycerol and sucrose. J. Membr. Biol. 15, 137-158. 

We optimized the growth of strain HXN-200 on n-octane and produced the cells in a large amount. It was found that the cells can be stored at — 80°C for two years without significant loss of activity. The frozen/thawed cells, that are easy to handle for the organic chemist, can be used for routine hydroxylation in an organic chemistry laboratory. 

To facilitate its application in organic synthesis, we developed a lyophilized cell powder of Sphingomonas sp. HXN-200 as a biohydroxylation catalyst. Hydro-xylation of A-benzyl-piperidine with such catalyst powder showed 85% of the activity of a similar hydroxylation with frozen/thawed cells, shown in Figure 15.6. The fact that rehydrated lyophilized cells are able to carry out such a reduced nicotinamide adenine dinucleotide (NADH)-dependent hydroxylation indicates that these cells are capable of retaining and regenerating NADH at rates equal to or exceeding the rate of hydroxylation. To our knowledge, this is the first example of the use of lyophilized cells for a cofactor-dependent hydroxylation. 

Figure 15.6 Hydroxylation of iV-benzylpiperidine (5 mM) with lyophilized cell powder and frozen/thawed cells of Sphingomonas sp. HXN-200 at cell concentration of 4.0 g cdw/L.

Fernandez et al. (2007) have characterized the rheological behavior of the mashed potatoes with added biopolymers using steady shear measurements. Fresh and frozen/thawed mashed potatoes present shear thinning with yield stress (Canet et al., 2005a), and dynamic shear data reveal weak gel-like behavior in potato purees (Alvarez et al., 2004). The effects are strongly... 

Alvarez, M. D., Canet, W. (1999h). Optimization of stepwise hlanching of frozen-thawed potato tissues (cv. Monalisa). Fur. Food Res. Techrwl., 210, 102-108. 

Note Following reconstitution, reagent should be used immediately. Any reagent remaining after reconstitution is stable at 2 to 8°C for 24 hours or for up to 1 month at -20°C or below. Reconstituted reagent can be frozen-thawed only once. Reconstituted reagent should be slightly opalescent. Yellow color indicates contamination or denaturation. Label vial with initials, date reconstituted, and expiration. 

Oprelvekin is supplied us a lyophili/ed powder for recon-.stitution. Excipients include glycine and phosphate buffer components. The powder has a shelf life of 24 months. It should be stored at 2 to 8°C. If it is frozen, thaw it before reconstitution. 

If reaction plates are frozen, thaw at room temperature. 

Preliminary experiments suggested that appreciable amounts of zinc in leukocytes are firmly bound to proteins, since only a very small fraction of the metal was found dialyzable. White cells from human subjects were frozen, thawed, diluted with distilled water, and then extracted with ether to remove lipids. The total white cells contained 13,000 uS-, the materials extracted by ether contained 39 /xg. of zinc, or 0.13% of the total zinc present. Investigations, therefore, centered on the zinc presumably bound to lipid-free protein. 

Electrocompetent yeast can be stored at -80°C for future use by adding glycerol to 15% final concentration and snapfreezing in a dry ice/ethanol bath. To use frozen cells, thaw slowly on ice, pellet the cells, and resuspended to the same volume in fresh, ice-cold 1M sorbitol. This will remove excess ions released by dead cells. The transformation efficiency using these frozen/thawed cells will drop > 10-fold from fresh yeast. 

Figure 2. Results from low voltage electrophoresis of the press juice from nonfrozen and frozen-thawed porcine muscle. Psoas muscle, excised 5 days postmortem and frozen at —20°C for 20 days. (Ordinate) GOT...

Differentiation Between Fresh and Frozen-Thawed Meat... 

This procedure also can be used to differentiate between fresh and frozen-thawed fish. In fresh, homogenized carp muscle we found four GOT isozymes—one sarcoplasmic and three mitochondrial (48). Upon freezing of whole carp, the mitochondrial isozymes (GOTmi, GOTM2, GOTM3) are released (Table VII) (49). Thus, press juice from fresh carp muscle exhibits one band, whereas after freezing and thawing four bands appear. 

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