Artifacts microscopy

Apart from the sheer complexity of the static stmctures of biomolecules, they are also rather labile. On the one hand this means that especial consideration must be given to the fact (for example in electron microscopy) that samples have to be dried, possibly stained, and then measured in high vacuum, which may introduce artifacts into the observed images [5]. On the other, apart from the vexing question of whether a protein in a crystal has the same stmcture as one freely diffusing in solution, the static stmcture resulting from an x-ray diffraction experiment gives few clues to the molecular motions on which operation of an enzyme depends [6]. 

Other artifacts that have been mentioned arise from the sensitivity of STM to local electronic structure, and the sensitivity of SFM to the rigidity of the sample s surface. Regions of variable conductivity will be convolved with topographic features in STM, and soft surfaces can deform under the pressure of the SFM tip. The latter can be addressed by operating SFM in the attractive mode, at some sacrifice in the lateral resolution. A limitation of both techniques is their inability to distinguish among atomic species, except in a limited number of circumstances with STM microscopy. 

The compensation birefringence measurement is very easily coupled to optical microscopy in the transmission and reflection modes, thus allowing characterizing orientation with a spatial resolution of a few hundreds of nanometers [14]. Polarizing microscopes are widely available and are often used for birefringence studies even if spatial resolution is not required. Objectives specifically designed for cross-polarized microscopy are necessary to avoid artifacts. 

Crang RFE, Klomparens KL. Artifacts in Biological Electron Microscopy, Plenum Press, New York, 1988, pp. 39-58. 

Transmission electron microscopy (TEM) can provide valuable information on particle size, shape, and structure, as well as on the presence of different types of colloidal structures within the dispersion. As a complication, however, all electron microscopic techniques applicable for solid lipid nanoparticles require more or less sophisticated specimen preparation procedures that may lead to artifacts. Considerable experience is often necessary to distinguish these artifacts from real structures and to decide whether the structures observed are representative of the sample. Moreover, most TEM techniques can give only a two-dimensional projection of the three-dimensional objects under investigation. Because it may be difficult to conclude the shape of the original object from electron micrographs, additional information derived from complementary characterization methods is often very helpful for the interpretation of electron microscopic data. 

Hecht, B., Bielefeldt, H., Inouye, Y, Pohl, D. W., and Novotny, L. 1997. Facts and artifacts in near-field optical microscopy. J. Appl. Phys. 81 2492-98. 

Since the work reported by McCartney et al. (9), ultrathin sections of other, more heterogeneous components and mixtures of components of coals of different rank have been prepared and observed. Procedures for minimizing artifacts have been learned and followed, and experience in observation has led to avoiding obvious faults. These sections were often not as large and continuous as those of homogeneous vitrinites, but adequate areas were available for electron microscopy. Observations of these various components revealed ultrafine structures of different size and form. Some of the structures can be correlated with those deduced from other direct or indirect study techniques others are unfamiliar and novel, and suggested interpretations are tentative. 

A variety of instruments and techniques exist for monitoring particle size. The most widely used techniques rely on laser light scattering, as reviewed by Tadros et al. (2004). Instruments manufacturers include Nicomp, Coulter, Horiba, Sympatec, and Malvern. Electron microscopy has also been used, but artifacts introduced by Lxing techniques should be carefully controlled. Typically, emulsions produced by the methods described above yield particle sizes of 100-1000 nm particle sizes less than 200 nm are generally required for emulsions used intravenously. 

As reported earlier, several types of microscopy techniques can be used for the observation of food microstructure. They allow the generation of data in the form of images (Kalab et al., 1995). Because of the artifacts due to the preparation of samples before microscopy analysis, it is advisable to apply a variety of techniques to the same samples in order to compare the... 

Kalab, M. 1984. Artifacts in conventional scanning electron microscopy of some milk products. Food Microstruct. 3(2), 95-111. 

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