Recognition by cro repressor protein of its specific DNA binding sites appears to occur via multidentate hydrogen bonds between amino acid side chains of the protein and base-pair atoms in the major groove of right-handed B-form DNA. Most of the sequence-specific interactions between cro and DNA, as well as a number of sequence-independent ones, are mediated by a two-alpha-helical unit which appears to be common to many proteins that regulate gene expression.

ABSTRACT.Purpose: There is evidence that ocular blood flow plays a critical role in the clinical course of glaucoma. Any reduction in ocular blood flow due to topical antiglaucoma treatment should therefore be avoided. This study aimed to evaluate the short-term effect of local latanoprost application on ocular hemodynamics. Methods: Intraocular pressure (IOP), ocular pulse amplitude (OPA), ocular pulse volume (OPV), systemic blood pressure, heart rate and the pulsatile component of ocular blood flow (POBF) were recorded using a pneumotonometer linked to the Langham Ocular Blood Flow System in 24 patients in a prospective, open-label study before and after 1 week of topical latanoprost application in both eyes. Twenty of the subjects had primary open-angle glaucoma and four had ocular hypertension. Results: After 1 week of latanoprost treatment, IOP decreased significantly 6.2 ∫ 2.9 mmHg in OD (P ∞ 0.001) and 6.2 ∫ 3.2 mmHg in OS (P ∞ 0.001). Pulsatile OBF increased significantly by 201.2 ∫ 167.4 mL/min in OD (P ∞ 0.001) and 203.8 ∫ 187.3 mL/min in OS (P ∞ 0.001). Ocular pulse amplitude and OPV showed statistically significant increases (P ∞ 0.05 and P ∞ 0.001 respectively). Blood pressure and heart rate did not change significantly. Conclusion: Our results indicate that 1 week after latanoprost application, POBF, OPA and OPV were significantly increased in the eyes treated. More information on the perfusion of the optic nerve head is needed before the relevance of these findings to optic nerve head blood flow can be interpreted correctly.

Fossil remnants of bacteria involved in the enhancement of manganese and iron rarely occur within the microstratigraphy of rock varnishes collected from warm desert environments, because varnish formation processes ultimately destroy these microfossils through remobilization of Mn-Fe and reprecipitation in a clay-mineral matrix. In contrast, Mn-Fe encrustations on budding bacteria commonly occur within varnishes that formed within just a century along the Erie Barge Canal, New York. Nanoscale imagery and elemental analyses reveal that these budding bacterial forms greatly enhance Mn, Fe, or both in encrustations surrounding hyphae and cells. The Mn and Fe precipitates have a granular texture on the scale of !1 nm to ∼10 nm. The precipitates also have a stringy texture, where strings are typically only a few nanometers wide. These in situ observations are consistent with expectations from studies of budding-bacteria cultures and with the polygenetic model of varnish formation. Given that the Erie Canal site presents the fastest known rate of varnishing, with typical thicknesses around 15 mm formed in a century, only one or two budding bacteria encrusting Mn-Fe oxides each year would be sufficient to generate the observed Erie Canal varnish. This contrasts with one bacterium growing every ∼400 y being needed to generate observed rates of varnishing in typical warm desert settings.

Crystals of the protein B-phycoerythrin from the red alga Porphyridium cruentum undergo twinning by merohedry in which the two members of the twin are related by rotation about (1,1,-1,0), a symmetry operation of the lattice but not of the crystals. Several methods are compared for estimation of the volume fractions of the two members of the twin so that measured data can be corrected for this twinning. The effect of these corrections on the final electron-density map is analyzed. Results show that when the volume fraction of the smaller crystal in a twinned specimen used for structure determination by multiple isomorphous replacement is 0-0.1, correction of diffraction data for twinning results in a small but significant improvement in the accuracy of the electrondensity map.

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