Artifacts and Practical Issues in Atomic Force Microscopy.

As with any other microscopic technique, in atomic force microscopy (AFM), problems can arise. Some of these happen due to improper use of the microscope by the operator, and some are due to particular characteristics of the sample. Some occur depending on the type of instrument, or from probe damage. Some of them are artifacts inherent in the technique. Knowledge of these issues is important for correct data acquisition and interpretation, and in many cases, training in AFM is inadequate. In this chapter we show examples of common artifacts in AFM and describe, where possible, how to overcome them. Other practical issues important for best practice in AFM operation, such as noise reduction and data processing, are also discussed.

Antibacterial activity of novel peptide derived from Cry1Ab16 toxin and development of LbL films for foodborne pathogens control.

Escherichia coli is one of the most common etiological agents of diarrhea in developing countries. The appearance of resistant E. coli prevents treatment of these infections. Biotechnological products incorporating antimicrobial peptides are currently being considered in applications to prevent intestinal infections by these bacteria. The aim of this study was to evaluate the antibacterial activity of the peptide PcL342-354C, which is derived from the toxin Cry1Ab16 from Bacillus thuringiensis, against E. coli strains. We also report the preparation, characterization and evaluation of the antibacterial activity of LbL films containing PcL342-354C. The results showed that the PcL342-354C peptide inhibited the growth of different strains of E. coli with minimal inhibitory concentration ranging from 15.62-31.25µg/mL and minimal bactericidal concentration was 250µg/mL, indicating a potential antibacterial activity. The morphology of an ITO/Cashew gum/PcL342-354C film was analysed using atomic force microscopy which showed an increase of roughness due to the increase in the number of layers. The LbL films showed significant antibacterial activity against E. coli NCTC 9001 in both conditions tested (10 and 20 bilayers). Our results indicate that the peptide exhibits an antibacterial potential that can be tapped to develop biomaterials with antibacterial activity for use against foodborne pathogens.