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Tham khảo tài liệu 'atomic force microscopy in cell biology episode 1 part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 184 Braga and Ricci Fig. 2. Atomic force pictures of Helicobacter pylori and E. coli. The bar at the bottom right of each picture corresponds to 500 nanometers. A Common morphology of H. pylori without exposure to antibiotic. B Example of the different perspectives obtained by means of computer processing C-E Different alterations induced in H. pylori by Imaging of Bacteria Treated With Antibiotics 185 5. Care must be taken when choosing the adhesive used for fixing the glass slide to the sample holder. Avoid using thick double-sided adhesive tape as this can expand for a long time after pressure and thus cause instability in the vertical position of the tip. The specially produced sticky tabs made by different manufacturers are fine. 6. To obtain the best results it is necessary to be thoroughly familiar with the characteristics of different cantilevers and tips how these can be used and how they suit to the different kinds of samples investigated. For high-resolution work tip sharpness is essential tip properties can vary significantly within the same batch of cantilevers. Fine tuning of the feedback loop and set point together with the chosen scan speed is critical for good surface tracking. 7. As mentioned above AFM offers different imaging modes for investigating the sample. There is the contact mode in which the tip of the probe makes soft physical contact with the sample which should be used with harder and stiffer materials than biological samples as it can easily give rise to undesirable effects as the result of tip-to-sample interactions Fig. 2L . Tip pressure can indent and deform the sample surface and lateral forces can stretch the sample drag away loosely bound fragments or even detach the whole bacterium from the substrate 3 . These drawbacks of the contact AFM mode are overcome by using the intermittent-contact mode also called tapping mode. In this case the AFM feedback loop constantly dampens the high-frequency oscillations of the vibrating .
