EQUIPMENT & ACCESSORIES CATALOG EDITION IV GLOW DISCHARGE SYSTEMS zzzGloQube® Plus (continued) The primary application of the GloQube® Plus is the hydrophilization (wetting) of carbon-coated TEM
support films and grids which otherwise have the tendency to be hydrophobic. Glow discharge treatment with air will make film surfaces negatively charged and hydrophilic and allow the easy spread of aqueous solutions. This and other processes are outlined below.
Glow Discharge Typical Processes Surface State
Hydrophilic Hydrophilic Hydrophobic** Hydrophobic** Air
Positive Positive
Negative Air* Alkylamine Methanol * Air followed by post-treatment with magnesium acetate by the user. ** Hydrophobic, as noted above, may represent a less hydrophilic sample of less than 90 degrees contact angle.
Contact angle left: positive discharge using methanol shows carbon grid less hydrophobic Contact angle right: negative discharge using amylamine shows carbon grid surface hydrophobic
Hydrophilic Hydrophiobic What is... Glow Discharge?
TEM images of the 20S human proteasome complexes, showing the effect of altering the surface charge of the carbon support film on the orientation of the protein. 2.5 nm of carbon film on Quantifoil® 400 mesh was used as a support for the sample.
1.2/1.3
Electric glow discharge is a type of plasma formed by passing a current at 100 V to several kV through a gas at low pressure (i.e. in a vacuum system). The main application of glow discharge in electron microscopy (EM) is to convert naturally hydrophobic ('water-hating') carbon-coated transmission electron microscopy (TEM) support grids into a hydrophilic ('water- loving') condition. Glow discharge treatment with air will make film surfaces negatively charged and hydrophilic and allow the easy spread of aqueous solutions.
Other treatments include:
Hydrophilic-positive treatment in air with magnesium acetate post-treatment to allow nucleic acid adhesion to carbon films.
Hydrophobic-positive treatment with alkylamine for proteins, antibodies and nucleic acids.
Hydrophobic-negative treatment in air for positively charged protein molecules, (e.g. ferritin and cytochrome c).
Carbon surface without glow discharge treatment.
Visible some side views of the protein due to uneven charge of the surface.
Carbon surface with air glow discharge biased top view orientation of the protein caused by uniform negative charge of the surface.
Biased-top views 20s
proteasome complex adsorption on in-air glow discharge modified carbon support TEM grids.
Carbon surface with amylamine glow discharge.
Biased side-view orientation of the protein caused by uniform positive charge on the surface.
Glow discharge can also be used for modifying surface, for example, to increase bond strength of polymers.
Glow discharges are sometimes considered to be 'imperfect' plasmas and cannot be used to plasma etch or plasma ash specimens their use mainly being confined to altering surface energies, not the removal of bulk material.
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Surface Charge Atmosphere Typical Applications Negative
Recommeded applications for the GloQube®
Plus:
• Hydrophilization and cleaning of TEM grids carbon support films* for better sample spreading
• Improved adhesion and orientation of proteins, nucleic acids and antibodies
Hydrophilisation and cleaning of carbon coated TEM grids
Nucleic acid adhesion to carbon films
Controlled orientation and improved adhesion of negatively charged proteins, antibodies and nucleic acids
Controlled orientation and improved adhesion of positively charged protein molecules (e.g. ferritin, cytochrome c)
• TEM grid preparation for nanoparticle studies
These products are for Research Use Only.
* Typically: Formvar® , Lacey Carbon, Holey Carbon, Continuous Carbon, Quantifoil®
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