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Enhanced cyan fluorescent protein (ECFP) and its variant Cerulean are genetically encoded fluorophores widely used as donors in FRET-based cell imaging experiments. First, we have confirmed through denaturation experiments that the double-peak spectroscopic signature of these fluorescent proteins originates from the indole ring of the chromophore. Then, to explain the improvement in the fluorescence properties of Cerulean compared to those of ECFP, we have determined the high-resolution crystal structures of these two proteins at physiological pH and performed molecular dynamics simulations. In both proteins, the N-terminal half of the seventh strand exhibits two conformations. These conformations both have a complex set of van der Waals interactions with the chromophore and, as our simulations suggest, they interconvert on a nanosecond time scale. The Y145A and H148D mutations in Cerulean stabilize these interactions and allow the chromophore to be more planar, better packed, and less prone to collisional quenching, albeit only intermittently. As a consequence, the probability of nonradiative decay is significantly decreased. Our results highlight the considerable dynamical flexibility that exists in the vicinity of the tryptophan-based chromophore of these engineered fluorescent proteins and provide insights that should allow the design of mutants with enhanced optical properties.

Lignins and their cross-linking to hemicelluloses detrimentally affect the cellulose-to-ethanol conversion of grass lignocelluloses. Screening appropriate grass cell walls and their compositional changes during the various steps of the process calls for a high-throughput analytical technique. Such a performance can be fulfilled by Fourier transform mid-infrared (FT-MIR) spectroscopy. In the present paper, a set of maize cell walls from mature stems were selected, including brown midrib samples. Lignin fractions were isolated by mild acidolysis to obtain a set of purified maize lignin standards. The lignin content and the percentage of lignin-derived p-hydroxyphenyl (H), guaiacyl (G), and syringyl (S) thioacidolysis monomers were determined. In addition, the composition of cell wall polysaccharides, as well as the amount of ester-linked p-coumaric (CA) and ferulic (FA) acids, was measured by wet chemistry. Partial least square (PLS) analyses were applied to infrared and chemical data of cell walls. The resulting models showed a good predictive ability with regard to the lignin content, to the frequency of S (or G) thioacidolysis monomers, and to the level of ester-linked CA of maize cell walls. The loading plots and regression coefficients revealed relevant infrared absorption bands.

Fluorescent proteins are the workhorses of biological molecular imaging. Important imaging modalities (such as polarization microscopy or FRET imaging) exploit anisotropic optical properties of fluorescent proteins. The anisotropy of optical properties of fluorescent proteins is described by a vector (the transition dipole moment, TDM) for single-photon absorption, and by a tensor (the absorptivity tensor) for two-photon absorption. Despite the importance of anisotropy of light absorption in fluorescent proteins for quantitative structural interpretation of many imaging experiments, relevant experimental data is very limited. Here we present the results of our optical measurements on crystals of representative fluorescent proteins, as well as mathematical interpretation of these results, yielding information on the orientation of TDMs and properties of absorptivity tensors of the investigated fluorescent protein molecules.

TRICHINOSIS is a parasitic infection most frequently involving striated muscle. Inadequately cooked pork is the most common source of acquisition, although wild animal flesh has been implicated in several cases. 1 Adulteration of "safe" meats with pork by common utensils or meat grinders contributes to the prevalence of the infection. The incidence of this disease has been gradually declining, and it is presently very infrequently encountered in this country. As a result, many physicians may not be aware of the diagnosis until late in the course of the disease. In 1976, there were 96 cases reported to the Center for Disease Control (CDC), only one of which occurred in Florida. 2 We describe here a patient demonstrating vague symptoms and laboratory data that could have been misleading. Report of a Case A 27-year-old man came to the Tampa (Fla) General Hospital emergency room complaining of fever, chills, and myalgias. The