X-Message-Number: 33078
Date: Thu, 25 Nov 2010 18:12:55 -0800 (PST)
From: 
Subject: Cryoprotection properties of salts of organic acids

Snip>

"When crystals are grown from solutions containing a sufficient concentration of
organic acid salts no additional cryoprotection is needed as the crystals can 
safely be frozen directly from the crystallizing buffers."


Acta Crystallogr D Biol Crystallogr. 2010 Jul;66(Pt 7):789-96. Epub 2010 Jun 19.

Cryoprotection properties of salts of organic acids: a case study for a 
tetragonal crystal of HEW lysozyme.

Bujacz G, Wrzesniewska B, Bujacz A. Institute of Technical Biochemistry, 
Technical University of Lodz, Poland.
Abstract

    Currently, the great majority of the data that are used for solving 
    macromolecular structures by X-ray crystallography are collected at 
    cryogenic temperatures. Selection of a suitable cryoprotectant, which 
    ensures crystal stability at low temperatures, is critical for the success 
    of a particular diffraction experiment. The effectiveness of salts of 
    organic acids as potential cryoprotective agents is presented in the 
    following work. Sodium formate, acetate, malonate and citrate were tested, 
    as were sodium potassium tartrate and acetate in the form of potassium and 
    ammonium salts. For each salt investigated, the minimal concentration that 
    was required for successful cryoprotection was determined over the pH range 
    4.5-9.5. The cryoprotective ability of these organic salts depends upon the 
    number of carboxylic groups; the lowest concentration required for 
    cryoprotection was observed at neutral pH. Case-study experiments conducted 
    using the tetragonal form of hen egg-white lysozyme (HEWL) confirmed that 
    salts of organic acids can successfully act as cryoprotective agents of 
    protein crystals grown from high concentrations of inorganic salts. When 
    crystals are grown from solutions containing a sufficient concentration of 
    organic acid salts no additional cryoprotection is needed as the crystals 
    can safely be frozen directly from the crystallizing buffers.
PMID: 20606259

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