Flash-freezing

The dry ice blaster is an effective and mess-free method for in-place cleaning that eliminates the need to disassemble machinery before it is cleaned. Compressed air propels tiny dry ice pellets at supersonic speeds so they flash freeze and then lift grime, paint, rust, mold, and other contaminants from metal surfaces. Pellets vaporize quickly into the air, leaving no wastewater or solvents, only the soiled contaminant to be swept up. 

Figure 11.16 is a cryo-TEM image of G10 PAMAM dendrimers in water. The cryo technique involves flash freezing of the dendrimer solution as a thin film on a grid and is described elsewhere [20]. Individual dendrimers appear to be organized into an array of single dendrimer thickness. While there are complicating factors due to the sample preparation, the picture is consistent with... 

It is often necessary to flash-freeze crystals in order to prevent radiation damage during preliminary characterization and data collection. Conducting X-ray... 

Protocol 15.5 Flash-freezing of cocrystals grown from PEGs or salts ... 

Distillation and flash-freezing processes both require the condensation of vapors. 

Where it may not be convenient, or possible, to immediately flash freeze a tissue sample, ethanol-preserved paraffin-embedded specimens may also be used for MALDI imaging.184 Thinner microtome sections can be cut from the frozen tissue following this treatment and this is an advantage where comparisons need to be made with traditional histological stains for light microscopy. 

After expression and purification, protein samples are often initially available as lyophilized solids, in which the proteins are correctly folded but in an amorphous arrangement with an isotropic distribution of orientations. This form of the protein may be used for NMR studies but the lack of water can significantly affect the strucmres of the individual protein molecules. One simple way to overcome this is to rehydrate the sample with small amounts of water." The effect can be quite significant, as illustrated in Fig. 2 for a sample of the 76-residue protein ubiquitin. Flash freezing offers the opportunity of preparing solid samples of proteins in which the solution-state structure is largely preserved." " ... 

The temperature dependence of has been investigated in detail with myoglobin [202]. Diffraction studies at four temperatures between 220 and 300 K show the structure to be composed of a condensed core around the haem with displacements of the order of 0.04 A, which are temperature sensitive, and a semiliquid region towards the outside with mean square displacements 0.04-0.25 A, which are essentially temperature independent. The movements of the surface residues point to a possible pathway to the haem group. More detailed analysis at 80 K with crystals cooled by flash-freezing without the use of cryoprotectants showed a decrease in overall B from 14 A at 300 K to 5 A at 80 K [203]. Analysis of individual temperature factors showed that 46 out of the 153 residues in myoglobin had average B factors that extrapolated to zero at 0 K (i.e., arose from thermal vibrations alone). The temperature vibration of the remainder of the protein was consistent with the notion that conformational substrates could be frozen out at low temperatures. An additional 51 residues could be modelled with a linear dependence on temperature but with... 

Many protein crystals can be cooled to 253 K (—20°C) without formation of ice crystals, but for studies at lower temperatures either flash freezing or the presence of a cryoprotectant is required. 

Flash freezing was pioneered by Haas and Rossmann [208] in their early studies on lactate dehydrogenase at 198 K (—75°C) and was also used in the recent studies on myoglobin at 80 K (- 193°C) [203]. In this method the crystals are plunged into either... 

Mouse plasma C57BL6 mouse plasma, mixed sex, lithium heparin anticoagulant (Sanford-Burnham Animal Facilities, La Jolla, CA, USA) (r eNote 1). Store aliquots at -20 °C. Store thawed aliquot on ice and flash-freeze the remaining blood sample at end of assay day. 

Alkaline phosphatase stock solutions are usually stable at 4 °C for a few weeks. For long-term storage it is recommended to flash freeze small aliquots of enzymes in liquid nitrogen and store at -80°C. 

Two famous American companies made major contributions to food preservation in the early 20th century. Clarence Birdseye, known as the "father of frozen food," adapted a method of freezing food that he learned from Eskimos meat frozen in the extreme cold of midwinter actually keeps better than any other preserved meat, frozen or otherwise. In 1923, he perfected the process of flash-freezing foods under high pressure, and the modern frozen food industry was born. 

Cap the vial, mix, flash freeze in liquid nitrogen and store at -80°C. 

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