Conjugation to the Cell-Penetrating Peptide TAT Potentiates the Photodynamic Effect of Carboxytetramethylrhodamine

Cell-penetrating peptides (CPPs) can transport macromolecular cargos into live cells. However, the cellular delivery efficiency of these reagents is often suboptimal because CPP-cargo conjugates typically remain trapped inside endosomes. Interestingly, irradiation of fluorescently labeled CPPs with light increases the release of the peptide and its cargos into the cytosol. However, the mechanism of this phenomenon is not clear. Here we investigate the molecular basis of the photo-induced endosomolytic activity of the prototypical CPPs TAT labeled to the fluorophore 5(6)-carboxytetramethylrhodamine (TMR).We report that TMR-TAT acts as a photosensitizer that can destroy membranes. TMR-TAT escapes from endosomes after exposure to moderate light doses. However, this is also accompanied by loss of plasma membrane integrity, membrane blebbing, and cell-death. In addition, the peptide causes the destruction of cells when applied extracellularly and also triggers the photohemolysis of red blood cells. These photolytic and photocytotoxic effects were inhibited by hydrophobic singlet oxygen quenchers but not by hydrophilic quenchers.Together, these results suggest that TAT can convert an innocuous fluorophore such as TMR into a potent photolytic agent. This effect involves the targeting of the fluorophore to cellular membranes and the production of singlet oxygen within the hydrophobic environment of the membranes. Our findings may be relevant for the design of reagents with photo-induced endosomolytic activity. The photocytotoxicity exhibited by TMR-TAT also suggests that CPP-chromophore conjugates could aid the development of novel Photodynamic Therapy agents

An array of low-background 3He proportional counters for theSudbury Neutrino Observatory

An array of Neutral-Current Detectors (NCDs) has been builtin order to make a unique measurement of the total active ux of solarneutrinos in the Sudbury Neutrino Observatory (SNO). Data in the thirdphase of the SNO experiment were collected between November 2004 andNovember 2006, after the NCD array was added to improve theneutral-current sensitivity of the SNO detector. This array consisted of36 strings of proportional counters lled with a mixture of 3He and CF4gas capable of detecting the neutrons liberated by the neutrino-deuteronneutral current reaction in the D2O, and four strings lled with a mixtureof 4He and CF4 gas for background measurements. The proportional counterdiameter is 5 cm. The total deployed array length was 398 m. The SNO NCDarray is the lowest-radioactivity large array of proportional countersever produced. This article describes the design, construction,deployment, and characterization of the NCD array, discusses theelectronics and data acquisition system, and considers event signaturesand backgrounds

Neurokinin B and pre-eclampsia: a decade of discovery

ABSTRACT: At the start of the last decade, we provided evidence that levels of the peptide neurokinin B were highly elevated in pre-eclampsia. We hypothesized that elevated levels of neurokinin B may be an indicator of pre-eclampsia and that treatment with certain neurokinin receptor antagonists may be useful in alleviating the symptoms. At the time of the original hypothesis many questions remained outstanding. These included - Does neurokinin B have any diagnostic value in the detection and diagnosis of pre-eclampsia? - What is the cause of the elevated levels of neurokinin B during pre-eclampsia? - What is the physiological significance of neurokinin B in the placenta? This review discusses the answers to these questions taking into account the subsequent developments of the past ten years and analyzing the plethora of discoveries that have arisen from those initial observations

Third trimester plasma neurokinin B levels in women with and without preeclampsia

Objective. This study was undertaken to measure neurokinin B (NKB) levels in pregnant women with and without preeclampsia (PE) in the third trimester. The study focused on the Black (sub-Saharan ancestry) and 'mixed ancestry' (synonymous with 'colored' and denotes an established race group of Khoisan, European, Malay, Malagascan, African, and South Indian ancestry) populations, constituting the majority of inhabitants of the Western Cape Province of South Africa. Methods. Questionnaires were used to obtain clinical data from pregnant 'mixed ancestry' and Black women. Third trimester plasma NKB levels were determined by enzyme-linked immunosorbent assay technique (EIA) in 72 pregnant women with PE and in 94 healthy women. The EIA results were then correlated with clinical data. Results. The mean NKB concentration in the PE groups (23.5 ng/L for 'mixed ancestry' and 15.0 ng/L for Black women) was significantly higher than in the control groups (3.8 ng/L and 4.4 ng/L, respectively; p ≤ 0.001). No significant differences in maternal clinical data were found between the diseased groups. Conclusions. Using the EIA technique, this study confirms previous reports of elevated NKB levels in the plasma of PE women in the third trimester. Whether increased NKB levels are causative or merely associated with PE remains unknown, as do the causative molecular mechanisms. Future longitudinal studies are certainly needed to further elucidate the predictive value of NKB in PE. © 2008 Informa UK Ltd.Articl