**Part 1**

**General Techniques** 

**1** 

*Italy* 

**Atomic Force Spectroscopies:** 

Michele Giocondo et al.\*

**A Toolbox for Probing the Biological Matter** 

*CNR-IPCF, Institute for Chemical and Physical Processes, National Research Council* 

Since its introduction in the early 1980's (Binnig et al., 1986), scanning probe microscopy (SPM) has shown its huge potential for the investigation of the matter at the micro- and nano- scale. In the following years, many variants have been introduced, exploiting electrostatic, magnetic or van der Waals-like forces acting between the sample surface and the probe. In the present chapter, we will be concerned with the latter, also known as atomic force microscopy (AFM). The heart of an atomic force microscope is a sharp tip attached to the extremity of a flexible cantilever, that interacts with the sample surface while the sample is scanned under the tip. The interaction forces between the tip and the sample cause the bending of the cantilever. When the sample is scanned under the tip, the tiny movements of the cantilever are detected by an optical lever system (a device for magnifying small angular displacements of a rotating body, exploiting the reflection of a fixed laser beam over a small mirror attached to the body) producing a spot of light whose position is measured, and they are used as the basis to reconstruct a pseudo-3D image of the sample surface. An atomic force microscope offers the possibility to operate in many different modes (namely: contact, non-contact and intermittent-contact modes), making this technique extremely versatile as it can be adapted to many classes of materials, from the solid state to the biological molecules. According to the sample stiffness, one can adopt the most suitable operating mode in order

Nowadays, AFM has proven as an essential tool for the analysis of microbial systems. Emerging methods have rapidly been implemented to make them available to biologists and there exists a great potential for future applications of this technique to biological systems. At the level of the whole cell, AFM has provided an integrated analysis of how the microbial cell exploits its environment through the cell surface. At the macromolecular level, AFM investigation into the properties of surface macromolecules and the energies associated with

to reduce or even prevent any damage of the observed specimen.

Said Houmadi1, Emanuela Bruno1,2, Maria P. De Santo1,2, Luca De Stefano3,

*1CNR-IPCF, Institute for Chemical and Physical Processes, National Research Council, Italy* 

*3CNR-IMM Institute for Microelectronics and Microsystems, National Research Council, Italy 4CNRS-INSP Institute of Nano-Sciences National Scientific Research Council, France 5Dept. of Organic Chemistry and Biochemistry, University of Naples "Federico II", Italy*

Emmanuelle Lacaze4, Sara Longobardi5 and Paola Giardina5

*2Department of Physics, Università della Calabria, Italy* 

**1. Introduction** 

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