Sonics VC750 (Serial No. "Y through "AB")" - Manual (Page 25)

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Detergent cell lysis is sometimes used in conjunction with ultrasonic processing to
facilitate disruption. Detergents break the lipid barrier surrounding cells by solubilizing
proteins and disrupting lipid:lipid, protein:protein and protein:lipid interactions.
Detergents, like lipids, self-associate and bind to hydrophobic surfaces. They are
composed of a polar hydrophilic head group and a nonpolar hydrophobic tail and are
categorized by the nature of the head group as either ionic (cationic or anionic),
nonionic or zwitterionic. Their behavior depends on the properties of the head group
and tail.
NOTE:
When working with detergents, do not use a probe with a replaceable tip. Use a solid
probe instead.
Unfortunately, there is no standard protocol available for selecting a detergent to use
for membrane lysis, the ideal detergent will depend on the intended application. In
general, nonionic and zwitterionic detergents are milder and less denaturing than ionic
detergents and are used to solubilize membrane proteins when it is critical to maintain
protein function and/or retain native protein:protein interactions for enzyme assays or
immunoassays. Zwitterionic detergents and nonionic detergents are commonly used
for these purposes. In contrast, ionic detergents are strong solubilizing agents and
tend to denature proteins, thereby destroying protein activity and function. There are
a few commonly used ionic detergents that are only mildly denaturing, including
sodium cholate and sodium deoxycholate.
The choice of detergent for cell lysis also depends on sample type. Animal cells,
bacteria and yeast all have differing requirements for optimal lysis due to the presence
of absence of a cell wall. Because of the dense and complex nature of animal tissues,
they require both detergent and sonication. In addition to the choice of detergent,
other important considerations for optimal cell lysis include the buffer, pH, salt
concentration and temperature. Consideration should be given to the compatibility of
the chosen detergent with downstream applications. For example, if the detergent
used for lysis must be removed, then a dialyzable detergent should be selected.
If pretreatment with enzymes or detergents cannot be used, the freeze / thaw method
should be considered. The freeze / thaw method is commonly used to lyse bacterial
and mammalian cells. The technique involves freezing a cell suspension for 10
minutes in a dry ice and isopropanol bath and then thawing the material at room
temperature immediately prior to ultrasonic processing. The freeze / thaw cycle
should be repeated three times prior to being subjected to the ultrasonics. This
method of lysis causes cells to swell and ultimately break as ice crystals form during
the freezing process and then contract during thawing. This pretreatment has been