Binding mode of a cationic porphyrin to parallel and antiparallel thrombin binding aptamer G-quadruplex.

The spectral properties of meso-tetrakis (N-methylpyridinium-4-yl)porphyrin (TMPyP) in the presence of parallel and antiparallel G-quadruplexes formed from a thrombin-binding aptamer G-quadruplex (5'-G3T2G3TGTG3T2G3) were investigated in this study. Red shift and hypochromism in the Soret absorption band of TMPyP were observed after binding to both parallel and antiparallel G-quadruplexes. The extent of changes in the absorption spectra were similar for both conformers. No circular dichroism spectrum was induced in the Soret region for both parallel and antiparallel G-quadruplexes. This is suggest that there is no or very weak interaction between electric transitions of nucleobases and porphyrin molecule. The accessibility of the neutral quencher I2 to the G-quadruplex-bound TMPyP was similar for both parallel and antiparallel G-quadruplexes. All these observations suggest that TMPyP was bound at the outside of the quadruplexes, and conceivably interacted with the phosphate group via a weak electrostatic interaction.Communicated by Ramaswamy H. Sarma.

A pilot study comparing 2 oxygen delivery methods for patients' comfort and administration of oxygen.

BACKGROUND: The traditional oxygen delivery methods for oxygen therapy are continuous flow oxygen (CFO) and demand oxygen delivery (DOD); however, oxygen waste is considerable in CFO, while DOD is uncomfortable for patients. Synchronized DOD (SDOD), which was designed to overcome the drawbacks of both CFO and DOD, supplies oxygen according to the patient's breathing pattern and the desired oxygen saving. This study was conducted to examine the overall performance of SDOD in terms of oxygen saturation (SpO2 ), patients' comfort, and oxygen saving ratio (SR). METHODS: Study subjects were patients who required oxygen for COPD or pneumonia. Patients received oxygen through nasal prongs by CFO and SDOD for 30 min each. SpO2 was measured every 10 min by pulse oximetry, and subjects recorded their level of comfort after 30 min. The flow of discharged oxygen was recorded to calculate SR. RESULTS: Ten subjects (median age, 68 y; range, 56-86 y) were enrolled. The SpO2 of patients during SDOD (97 ± 2%) was similar to that during CFO (96 ± 3%) with no statistically significant difference (P = .53). Subjects reported SDOD to be more comfortable than CFO. The comfort score of subjects treated with SDOD was 7.05 ± 2.07 (0: very uncomfortable, 10: very comfortable); this was significantly higher (P = .02) than the comfort score (5.20 ± 1.83) of subjects treated with CFO. The SR values set by clinicians were very similar to calculated SR values. CONCLUSIONS: SDOD appears to be more suitable for oxygen therapy than CFO when considering SpO2 , patients' comfort, and SR.

Synchronization of oxygen delivery with breathing pattern for enhanced comfort: a bench study.

BACKGROUND: Oxygen has been widely used for COPD patients because long-term oxygen therapy can improve survival duration of COPD patients with severe hypoxemia. The typical oxygen delivery methods used for long-term oxygen therapy are continuous flow oxygen (CFO) and demand oxygen delivery (DOD). Currently, DOD is preferred to CFO in oxygen conserving devices because waste of oxygen is substantial in CFO. However, DOD causes discomfort to patients since it abruptly supplies high-flow oxygen during inhalation only. METHODS: To overcome the drawbacks of CFO and DOD, we developed a novel oxygen delivery method, synchronized DOD (SDOD), which can reduce waste oxygen and patient discomfort. We used the concept of "jerk" from physics, which indicates the rate of change of acceleration, and defined a discomfort index (DI) to quantitatively represent the degree of discomfort. To determine the correlation between DI and the actual human feeling of discomfort, we tested subjects' responses to different levels of DI. Moreover, depending on the level of oxygen saving of each method, CFO, DOD, and SDOD regions were identified in a prescription flow/supply flow plane. A bench study was conducted to experimentally compare the Fio2 between CFO and SDOD at 20 breaths/min. RESULTS: The results of this study illustrate that there is a region of compromise between oxygen saving and patient comfort that is filled by SDOD. DI is positively correlated with actual human discomfort (P < .001). In addition, the DI of SDOD was much lower than that of DOD. Fio2 of SDOD was 2-5% less than that of CFO. CONCLUSIONS: In conclusion, SDOD might provide more comfortable oxygen delivery by reducing DI, and conserves oxygen while offering an equivalent Fio2.

Real-time detection of Fe.EDTA/H2O2-induced DNA cleavage by linear dichroism.

The conditions for the measurement of linear dichroism (LD) can be adjusted so as to solely reflect the length and the flexibility of DNA. The real-time detection of the EDTA.Fe(2+)-induced oxidative cleavage of double-stranded native and synthetic DNAs was performed using LD. The decrease in the magnitude of the LD at 260 nm, which reflects an increase in the flexibility and a decrease in the length of the DNA, can be described by the sum of two or three exponential curves in relation to the EDTA.Fe(2+) concentration. The fast component was assigned to the cleavage of one of the double strands, inducing an increase in the flexibility, while the other slower component was assigned to the cleavage of the double strand, resulting in the shortening of DNA. The decrease in the magnitude of the LD of poly[d(A-T)(2)] was similar to that of poly[d(I-C)(2)], while that of poly[d(G-C)(2)] was found to be the slowest, indicating that the resistance of poly[d(G-C)(2)] against the Fenton-type reagent was the strongest. This observation suggests that the amine group in the minor groove of the double helix may play an important role in slowing the EDTA.Fe(2+)-induced oxidative cleavage.