Infrared freeze-drying

S. J. Perstrelski, T. Arakawa, and J. F. Carpenter, Separation of freezing and drying-induced denaturation of lyophilized proteins using stress-specific stabilization. II. Structural studies using infrared spectroscopy, Arch. Biochem. Biophys., 303, 465... 

Remmele et al. [3.55] studied with infrared spectroscopy the structure-hydration behavior of a 49.4 mg/mL lysozyme D20 solution with and without 10 % sucrose. The sample was cooled n in the measuring chamber to -100 °C and then connected to a freeze drying installation, after which the temperature of the sample was raised to +40 °C ... 

I.R. Last and K.A. Prebble, Suitabihty of near-infrared methods for the determination of moistnre in a freeze-dried injection prodnct containing different amonnts of the active ingredient, J. Pharm. Biomed. Anal., 11(11/12), 1071-1076 (1993). 

M.W.J. Derksen, P.J.M. Van De Oetelaar and F.A. Maris, The use of near-infrared spectroscopy in the efficient prediction of a specification for the residual moisture content of a freeze-dried product, J. Pharm. Biomed. Anal., 17, 473 80 (1998). 

The total solid (dry matter) content of potato can be obtained by freeze-drying. Dry matter content is determined from the difference in the weight of potato samples before and after freeze-drying. The potato dry matter can also be estimated from the specific gravity measurements. In recent years, near infrared (NIR) spectroscopy has been used to measure specific gravity of potatoes. The NIR spectra (700-1100 nm) of potato samples are acquired, and partial least squares (PLS) regression analysis can be used to develop a predictive model for specific gravity (Scanlon et al., 1999). 

Other fire protection features have been incorporated into CNG refueling facilities such as methane detectors to warn of leaks from the dispenser, and automated fire suppression systems activated by ultraviolet/infrared detectors. Dry chemical is the preferred fire suppression material since water line protection from freezing is difficult in outdoor settings. The methane detectors can also be used to shut down the compressor and dispenser if desired. 

Jones, J.A., Last, I.R., MacDonald, B.F. and Prebble, K.A. (1993) Development and transfer-ability of near-infrared methods for determination of moisture in a freeze-dried injection product /. Pharm. Biomed. Anal. 11, 1227-1231. 

Two grams of HSPAN was added to 500 ml of water, the pH was adjusted from 9 to 6.5 with dilute hydrochloric acid, and 0.1 ml of Thermamyl 60L enzyme solution (Novo Enzyme Corp.) was added. The resulting mixture was heated at 95°C for 21 hr, and the clear yellow solution was exhaustively dialyzed against distilled water. Freeze drying yielded 1.235 g of polymer, which contained only about 5% residual carbohydrate (by infrared analysis). The number average molecular weight of this polymer was 44,000, as determined in 0.15N sodium chloride solution on a Melabs Model CSM-2 membrane osmometer equipped with a B-19 membrane (Schleicher and Schuell Co.). 

All reactions and sample preparations are carried out in an inert-atmosphere enclosure under dry nitrogen. Solvents and reagents are dried in the following manner. Benzene, tetrahydrofuran, and n-pentane are freshly distilled from lithium aluminum hydride pyridine is distilled over barium oxide and tetramethylethylenediamine is distilled over calcium hydride. Solvents used in preparing nmr and infrared samples are degassed by a freeze-thaw technique. Nmr spectra are obtained with torch-sealed nmr tubes. The commercial transition metal carbonyl complexes are recrystallized and vacuum-dried before use. Glassware is routinely flame-dried. 

The practical solution to the protein stability dilemma is to remove the water. Lyophilization (freeze-drying) is most commonly used to prepare dehydrated proteins, which, theoretically, should have the desired long-term stability at ambient temperatures. However, as will be described in this review, recent infrared spectroscopic studies have documented that the acute freezing and dehydration stresses of lyophilization can induce protein unfolding [8-11]. Unfolding not only can lead to irreversible protein denaturation, even if the sample is rehydrated immediately, but can also reduce storage stability in the dried solid [12,13]. 

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