The high specificity in the recognition and specific binding of potassium ion by the depsipeptide valinomycin (VM) is exploited for its recognition and quantitation using both circular dichroism (CD) and optical rotation dispersion (ORD). The specific rotation of VM is comparably small (2.34 deg ml g(-1) cm(-1)), so that an 8 microM (= 8.89 mg ml(-1)) solution of VM in 95% ethanol rotates polarized light of Lambda = 426 nm passing a 2 cm cuvette by 0.076 degrees only. It is shown, however, that VM undergoes large changes in both ORD and CD on binding to potassium ion. VM, potassium ion and the anionic dye merocyanine 540 form a ternary complex (VM/K/MC) which displays an induced CD with a positive maximum at 488 nm and a negative maximum at 470 nm. The ternary complex also displays fluorescence that is weaker by about 30% when compared to that of the dye alone. The induced CD of the ternary complex is interpreted in terms of the large conformational change which VM is known to undergo on binding potassium ion, thereby forming the prerequisite for a van der Waals interaction between its outwardly directed lipophilic domains and the lipophilic domains of the anionic dye. The method is likely to be applicable to the fluorescent detection of all kinds of ions for which chiral receptors are known, e.g. in studies on the role of ions in biological systems including ion channels.

Benzenesulfonates↗

PubMedDate not supplied

Optical sensor for seawater salinity.

An optical sensor for the measurement of salinity in seawater has been developed. It is based on a chloride-quenchable fluorescent probe (lucigenin) immobilized on a Nafion film. Two approaches for measuring salinity via chloride concentration are presented. In the first, a change in salinity corresponds to a change in the fluorescence intensity of lucigenin. In the second, the fluorescence intensity information is converted into a phase angle information by adding an inert phosphorescent reference luminophore (a ruthenium complex entrapped in poly(acrylonitrile) beads). Under these conditions, the chloride-dependent fluorescence intensity of lucigenin can be converted into a chloride-dependent fluorescence phase shift which serves as the analytical information. This scheme is referred to as dual lifetime referencing (DLR). The sensor was used to determine the salinity in seawater and brackish water of the North Sea.

Journal Article↗

PubMedDate not supplied

A medical workstation for the evaluation of alternative 3D radiotherapy treatment plans.

A medical workstation for the evaluation of alternative 3D radiotherapy plans is described. Our system can simultaneously apply qualitative as well as quantitative evaluation methods to as many as three 3D dose distributions. The user interface of the workstation has been designed with the demands of radiation oncologists in mind. The handling of the large amounts of 3D data (CT data, up to three 3D dose distributions, volumes of interest) is assisted by computer graphics.

Computer Graphics↗

PubMedDate not supplied

[Evaluating the pregnant cervix uteri by ultrasound with computer-assisted texture analysis].

BACKGROUND: Cervical ripening during pregnancy is associated with ultrastructural alterations, presumably correlated with structural changes of the ultrasonographic image. Analysing these changes might allow conclusions on cervical consistence without necessarily performing manual examination. PATIENTS AND METHODS: Ultrasound findings of 112 patients with normal pregnancy (14th to 41st week of pregnancy) have been compared to those of 57 patients admitted because of cervical insufficiency (20th to 35th week). A representative region of interest was analysed using a computer based texture analysing system ("Ultra" written in "Interactive Data Language"). 125 parameters derive from various texture algorithms: 1st order gray scale statistics, row, slit and area statistics, gradient statistics, cooccurrence statistics. By means of factor and multiple regression analysis those parameters could be determined, which contribute significantly to the clinical assessment of cervical consistence. Weighting these parameters a so called texture score (TS) and--implementing the other parameters of the Bishop-Score (BS)--a texture based cervical score (TBCS) could be established. RESULTS: Manual assessment of cervical consistence could be reproduced excellently by noninvasive texture analysis. TBCS was highly correlated to BS, correlation to remaining duration of pregnancy (RDOP) was highly significant for TBCS but insignificant for BS. CONCLUSIONS: Manual assessment of cervical consistence may be replaced by noninvasive texture analysis. Using RDOP as target parameter TS and TBCS turn out to be superior to manual assessment and BS respectively. DISCUSSION: Computer aided texture analysis of cervical ultrasound imaging provides a useful information, which can be obtained easily and might help to reduce palpatory controls and increase the accuracy of prediction of pregnancy prolongation.

Adult↗