Coincidence of the molecular organization of beta-substituted oligothiophenes in two-dimensional layers and three-dimensional crystals

The molecular arrangements of three different alkyl-substituted oligothiophenes both in two-dimensional adsorbed layers at a substrate interface and in bulk three-dimensional crystals were studied. Scanning tunneling microscopy (STM) was used to investigate the ordering of the conjugated oligomers in two-dimensional layers adsorbed on graphite. These data were compared with the X-ray structure determinations of single crystals revealing the arrangement in the three-dimensional bulk material. Quaterthiophenes 1 and 2, bearing dodecyl and hexyl side chains, respectively, exhibit a lamella-type stacking of the conjugated backbone concomitant with an interlocking of the alkyl side chains both on the surface and in the crystal. In contrast, the arrangement of propyl-substituted quaterthiophene 3 is rather "herringbone-like" due to the reduced interactions of the shorter alkyl side chains. In all three cases, evidently, the two-dimensional ordering at the graphite surface is coincident with the molecular packing in one cross-section of the three-dimensional crystal.

Stromal invasion by carcinoma of the cervix: assessment with dynamic MR imaging.

OBJECTIVE: The purpose of this study was to evaluate dynamic MR imaging in assessing the depth of stromal invasion by carcinoma of the cervix and to compare dynamic MR imaging with T2-weighted and contrast-enhanced T1-weighted MR imaging. SUBJECTS AND METHODS: Forty-one patients with carcinoma that was clinically considered to be confined to the cervix were examined with T2-weighted, dynamic, and contrast-enhanced T1-weighted MR imaging before surgery. We evaluated enhancement patterns of the cervix and tumor and assessed the degree of stromal invasion with MR imaging. The degree of stromal invasion was divided into two groups: superficial disease (no stromal invasion or invasion of < or = 3 mm) and deep invasion (> 3 mm of stromal invasion). Then we compared these MR findings with histologic results for the depth of stromal invasion. RESULTS: With dynamic MR imaging, cervical carcinoma with deep invasion was seen as a focal enhanced area in the early dynamic phase. The cervical epithelium and stroma enhanced less vividly. In distinguishing deep invasion from superficial disease, we found the accuracy of T2-weighted MR images, dynamic MR images, and contrast-enhanced T1-weighted MR images to be 76%, 98%, and 63%, respectively. In particular, the detectability of 3.1-5.0 mm of stromal invasion with dynamic MR images was significantly higher than that with the other techniques: with T2-weighted MR images, we saw 3.1-5.0 mm of stromal invasion in 23% of patients; with dynamic MR images, in 92%; and with contrast-enhanced T1-weighted MR images, in none. Superficial disease was not revealed with any of the three MR techniques. CONCLUSION: We believe that dynamic MR imaging is superior to T2-weighted MR imaging and contrast-enhanced T1-weighted MR imaging when assessing the depth of invasion of cervical carcinoma.

Thin film formation by rough form lipopolysaccharide and interaction with cationic antibiotic polymyxin B.

A monolayer film of the rough form of lipopolysaccharide (LPS) from Erwinia carotovora at an air-water interface was transferred onto solid substrates to form a multilayer film. The LPS was deposited on hydrophobic graphite as well as on hydrophilic platinum plates. The thickness of the LPS film prepared by a single dipping and removal of the graphite was estimated at 2.7 nm by atomic force microscopy. The repeated dipping of the platinum plate indicated early saturation with reduced subsequent absorption from the pure water subphase, while successive transfers of the LPS were observed from a 2.0 mM MgCl2 solution. The LPS film on the quartz crystal microbalance (QCM) interacted with cationic antibiotic polymyxin B in the solution and exhibited a downward shift of resonant frequency and resistance in proportion to its concentration. The resonant resistance change against the resonant frequency axis was parallel in this interaction. The absorption of the antibiotic on the LPS film prepared in the presence of MgCl2 indicated an increase in mass, but little change in viscoelasticity. A multilayer film of LPS on the QCM was found suitable for subsequent characterizations.