Frequently Asked Questions

Why the flat carbon film is important for collection the high resolution data?

 

High resolution 3D density map is helpful to understand the relationship between the molecular structure and function. A high resolution 3D density map relies on the high resolution data collection of molecules. The high quality data collection depend on the conditions of electron microscope, as well as the quality of specimens. The quality of grids is one of the important factors which affect the quality of specimens. For examples, the quality of grid could affect the flatness of carbon film, ice thickness and  breakage rate of the carbon film on holes.
 

What could cause the carbon film lack of flat?

 

Lack of flatness can be due to (1) Folding of the films causes by the Improper thermal expansion between the grid metals and Carbon film. (2) Rough edge of the grid holes. (3) Small particles trapped between the support film and the crystal

 

Why do I need molybdenum grids for 2D crystals of cryo-EM?

 

First of all, take a look following table

Metals vs. Carbon Thermal Parameters

 

 

Coefficient of linear
thermal expansion
[/K-1 multiplied by 106]

Electrical resistivity

[/10-8 Ωm; or mΩ cm]

Thermal conductivity
[/W m-1 K-1]

C

Carbon

7.1

~ 1000

140

Mo

Molybdenum

4.8

5

139

Cu

Copper

16.5

1.7

400

Fe

Iron

11.8

 9.7

80

Ti

Titanium

8.6

40

22

W

Tungsten

4.5

5

170

Au

Gold

14.2

2.2

320

Al

Aluminum

23.1

2.65

235

Ni

Nickel

13.4

7

91

Zn

Zinc

30.2

5.9

120

Pd

Lead

28.9

21

35

Ag

Silver

18.9

1.6

430

Ru

Ruthenium

6.4

7.1

120

Criteria: Ideal materials should have smaller electrical resistivity, larger thermal conductivity and closer thermal expansion coefficient to Carbon.

 

The ideal materials for cryo-grids should has the similarity coefficient of linear thermal expansion, since the different of thermal expansion between the carbon film and grid materials will result the cryo-wrinkle (if materials thermal expansion is greater than that of carbon) or broken of carbon film (if materials thermal expansion is less than that of carbon). You can find the Mo, Ti, W, Ru have the similar value as carbon.

 

In additional, the materials should be a better in both electron and thermal conductivity. Ti is poor in this value. Therefore, the ideal materials for cryo-EM are Mo, W, Ru. Ru is very expensive metal and W is hard to made as grid. Therefore, the only materials is Molybdenum.

 


Then, let take a look what experts talk about the materials of cryo-grids.

 

“… Measurements on grids made of titanium, molybdenum and tungsten showed significantly less puckering.”

-- Booy F.P. etc., Cryo-crinkling: what happens to carbon films on copper grids at low temperature. Ultramicroscopy. 48(1993)3,  273-80

 

“One of the main problems in data collection of 2D protein crystals for EM is a lack of flatness of the specimens. The resulting overlap of data from crystal areas of slightly different tilt angles (visible as blurring of the diffraction spots in the direction perpendicular to the tilt axis) is especially severe at high tilt angles and effectively reduces the vertical resolution of a 3-D map.”

-- Vonck, J., Parameters affecting specimen flatness of two-dimensional crystals for electron crystallography, Ultramicroscopy, 5(2000) 123-129.

 

What the problem will the un-flat carbon film cause?

 

(1) lost high resolution information.

from flat carbon film from un-flat carbon film

 

(2) Un-uniform ice thickness.

 

 

What cause the breakage of carbon film?

 

Breakage of carbon film on the grid holes caused by the rough edge of holes
Note: Same C-film on Mica floated on grids from diffract companies, and check on EM at same day.

 

Why the smooth surface of grid is important?

“... the use of molybdenum grids has become standard in electron cryo-microscopy. However, … the rough surface of these grids can also induce the carbon film to crinkle…” 

-- Fujiyoshi Y., The structural study of membrane proteins by electron crystallography, Adv. Biophysics, 35(1998) 25-80.

 

Why Pacific Grid-Tech's grids is best?

 

"Using the same preparation method with a batch of Pacific grid-Tech 300 mesh molybdenum grids, there was a much higher number of crystals that did not show any obvious signs of folds or wrinkles…"

 -- Vonck J., Ultramicroscopy, 85(2000) 3, 123-129.

Reference 1:

Abstract

Full Paper (PDF)

Reference 2:

Abstract

Full Paper (PDF)

 

What's the different of molybdenum grids between Pacific Grid-Tech and other companies' product?

 

Check our home page, http://www.grid-tech.com/

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Why is copper grids not suitable for 2-D crystals?

 

The thermal expansion is quit different with carbon film. This will result the carbon film wrinkle in low temperature. The winkle carbon film will result the protein distortion and high resolution information lost.

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How many scientist use Pacific grid-Tech's grids?

Please visit our clients page.

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How to order or purchase  it?

Please  click here for more information

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I have some questions, how can I contact with you?

Please email us at info@grid-tech.com, or call us at (800) 945 4743.

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How to storage grids?

Keep the grids into a desiccators for storage at room temperature.

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How to clean Mo grids before I use it?

Before floating carbon film onto grids, please clean grid in following procedure
1. Using Millipore water to wash it with super sonic for 3-5 minutes. During super sonic, keep shaking the grid bottle.
2. Using 99.99% acetone to wash supersonic the grids for about 3 minutes. Shaking of glasses bottle is needed during super sonic.
3. Using Millipore water to wash it again.
4. Put grids into 30% sulfuric acid, and wash them with shaking of the grid bottle in super sonic container.
5. Wash it again by Millipore water.
6. Using 99.99% acetone to wash grids again
7. It is ready to use after Millipore water washed.

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What should I be careful during use it?

Do NOT keep the cleaned grids in water for more than one hour since it can be etched by water.

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Why should I clean the grids hardly?

Well-cleaned grids results well contact between carbon film and surface of grid, also results the minimum charge affect when the electron beam hits on the cryo-specimen in EM. The protocol of cleaning is worthy to be followed because it could clean out dirt and oxidized layer on the surface of grids.

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