Enhancement of DNAzymatic activity using iterative in silico maturation.

DNAzyme-based (catalytic nucleic acid) biosensing technology is recognised as a valuable biosensing tool in diagnostic medicine and seen as a cheaper, more stable alternative to antibodies or enzymes. However, like enzyme discovery, no method exists to predict DNAzyme sequences that result in high catalytic activity using computer software (in silico). In this work, iterative in silico maturation and in vitro evaluation were applied to a DNAzyme oligodeoxynucleotide (ODN) sequence to elucidate novel synthetic sequences with enhanced DNAzyme activity. An already well-known model DNAzyme, the G-quadruplex/hemin complex, was iterated over eight generations to elucidate synthetic sequences that were up to five times faster than the original parent sequence. By combining molecular dynamics simulations, we found that the POD-mimicking activities were largely affected by docking modes and the tightness of locking between complexes. Ultimately, the theoretical models showed significant sequence-dependencies.

G-quadruplex-forming aptamer enhances the peroxidase activity of myoglobin against luminol.

Aptamers can control the biological functions of enzymes, thereby facilitating the development of novel biosensors. While aptamers that inhibit catalytic reactions of enzymes were found and used as signal transducers to sense target molecules in biosensors, no aptamers that amplify enzymatic activity have been identified. In this study, we report G-quadruplex (G4)-forming DNA aptamers that upregulate the peroxidase activity in myoglobin specifically for luminol. Using in vitro selection, one G4-forming aptamer that enhanced chemiluminescence from luminol by myoglobin's peroxidase activity was discovered. Through our strategy-in silico maturation, which is a genetic algorithm-aided sequence manipulation method, the enhancing activity of the aptamer was improved by introducing mutations to the aptamer sequences. The best aptamer conserved the parallel G4 property with over 300-times higher luminol chemiluminescence from peroxidase activity more than myoglobin alone at an optimal pH of 5.0. Furthermore, using hemin and hemin-binding aptamers, we demonstrated that the binding property of the G4 aptamers to heme in myoglobin might be necessary to exert the enhancing effect. Structure determination for one of the aptamers revealed a parallel-type G4 structure with propeller-like loops, which might be useful for a rational design of aptasensors utilizing the G4 aptamer-myoglobin pair.

Risk factors and survival impact of readmission after single-unit cord blood transplantation for adults.

Hospital readmissions have been used as a prognostic indicator for patients receiving allogeneic hematopoietic cell transplantation (HCT). However, the impact of readmission during early and mid-phase of cord blood transplantation (CBT) on long-term outcomes has not been fully investigated. We retrospectively analyzed 156 adult patients who received single-unit CBT in our institute. Among this cohort, thirteen patients (8%) were readmitted within 30 days after discharge, and 27 (17%) were readmitted within 90 days after discharge. The most common causes for readmission within 30 and 90 days of discharge were infection, chronic graft-versus-host disease, and relapse. Higher cryopreserved cord blood CD34+ cell count was only significantly associated with lower readmission within 90 days after discharge. The probabilities of overall survival were significantly lower in patients readmitted within 90 days after discharge compared with those who were not readmitted within 90 days after discharge in univariate and multivariate analysis. These data suggest that readmission within 90 days after discharge may have a significant impact on long-term mortality after single-unit CBT.

Risk factors and characteristics of falls among hospitalized adult patients with hematologic diseases.

OBJECTIVES: Falls and fall-related injuries are major problems in hospitals. In hematologic patients, both disease and its treatment, including chemotherapy and allogeneic hematopoietic cell transplantation (allo-HCT), can cause anemia, febrile neutropenia, and bleeding tendency, which may result in falls and fall-related injuries. MATERIALS AND METHODS: We retrospectively analyzed 397 consecutive admissions to the hematology unit at our institute which included 201 adult patients with hematologic disease. RESULTS AND CONCLUSIONS: A total of 56 fall events were observed in 43 patients, and the incidence of falls was 2.49 per 1000 person-days. The median hemoglobin, platelet, and serum albumin levels prior to fall events were 8.65g/dl (range, 6.3-12.7), 38×109/l (range, 7-454), and 2.85g/dl (range, 1.6-4.3), respectively. Despite the presence of thrombocytopenia among the majority of patients who fell, no serious injury was observed. Multiple variable logistic regression analysis demonstrated that age older than 65years (hazard ratio [HR], 2.86; 95% confidence interval [CI], 1.17-6.99, P=0.02), admission for allo-HCT (HR, 9.48; 95% CI, 3.35-26.80, P<0.001), hypnotic medication (HR, 3.57; 95% CI, 1.56-8.20, P=0.002), urinary or intravenous catheter placement (HR, 2.34; 95% CI, 1.08-5.09, P=0.03), and hypoalbuminemia (HR, 2.30; 95% CI, 1.07-4.96, P=0.03) were significantly associated with increased fall risk. These findings indicated that special attention should be paid to patients with such risk factors during their treatment.

Convection patterns in a liquid metal under an imposed horizontal magnetic field.

We performed laboratory experiments of Rayleigh-Bénard convection with liquid gallium under various intensities of a uniform imposed horizontal magnetic field. An ultrasonic velocity profiling method was used to visualize the spatiotemporal structure of the flows with simultaneous monitoring of the temperature fluctuations in the liquid gallium layer. The explored Rayleigh numbers Ra range from the critical value for onset of convection to 10(5); the Chandrasekhar number Q covers values up to 1100. A regime diagram of the convection patterns was established in relation to the Ra and Q values for a square vessel with aspect ratio 5. We identified five flow regimes: (I) a fluctuating large-scale pattern without rolls, (II) weakly constrained rolls with fluctuations, (III) a continuous oscillation of rolls, (IV) repeated roll number transitions with random reversals of the flow direction, and (V) steady two-dimensional (2D) rolls. These flow regimes are classified by the Ra/Q values, the ratio of the buoyancy to the Lorentz force. Power spectra from the temperature time series indicate that regimes I and II have the features of developed turbulence, while the other regimes do not. The region of steady 2D rolls (Busse balloon) extends to high Ra values in the present setting by a horizontal magnetic field and regime V is located inside the Busse balloon. Concerning the instabilities of the steady 2D rolls, regime III is the traveling wave convection developed from the oscillatory instability. Regime IV can be regarded as a state of phase turbulence, which is induced by intermittent occurrences of the skewed-varicose instability.

Spontaneous flow reversals in Rayleigh-Bénard convection of a liquid metal.

We report a finding of spontaneous flow reversals of roll-like patterns in liquid gallium Rayleigh-Bénard convection. The vessel has a square geometry with an aspect ratio of 5, and a horizontal magnetic field is applied to align the rolls. The flow patterns were visualized by ultrasonic velocity measurements, and the processes of the reversal were clearly observed. The basic flow pattern observed in the vessel is a four-roll structure with its axis parallel to the magnetic field. Emergence of a new circulation at a corner of the vessel causes flow reversal with reorganization of the whole pattern. The flow keeps relatively steady four-roll structure for most of the duration, while the reversal of it is over in a short time. The reversals of the flow occur randomly with the interval time between reversals being much longer than the circulation time.

Structure of large-scale flows and their oscillation in the thermal convection of liquid gallium.

This investigation observed large-scale flows in liquid gallium and the oscillation with Rayleigh-Bénard convection. An ultrasonic velocity profiling method was used to visualize the spatiotemporal flow pattern of the liquid gallium in a horizontally long rectangular vessel. Measuring the horizontal component of the flow velocity at several lines, an organized roll-like structure with four cells was observed in the 1×10(4)-2×10(5) range of Rayleigh numbers, and the rolls show clear oscillatory behavior. The long-term fluctuations in temperature observed in point measurements correspond to the oscillations of the organized roll structure. This flow structure can be interpreted as the continuous development of the oscillatory instability of two-dimensional roll convection that is theoretically investigated around the critical Rayleigh number. Both the velocity of the large-scale flows and the frequency of the oscillation increase proportional to the square root of the Rayleigh number. This indicates that the oscillation is closely related to the circulation of large-scale flow.

Detailed investigation of thermal convection in a liquid metal under a horizontal magnetic field: suppression of oscillatory flow observed by velocity profiles.

Thermal convection experiments in a liquid gallium layer were carried out with various intensities of uniform horizontal magnetic fields. The gallium layer was in a rectangular vessel with a 4:1:1 length ratio (1 is the height), where the magnetic field is applied in the direction normal to the longest vertical wall. An ultrasonic velocity profiling method was used to visualize the spatiotemporal variations in the flow pattern, and the temperature fluctuations in the gallium layer were also monitored. The observed flow pattern without a magnetic field shows oscillating rolls with axes normal to the longest vertical wall of the vessel. The oscillatory motion of the flow pattern was suppressed when increasing the applied magnetic field. The flow behavior was characterized by the fluctuation amplitude of the oscillation and the frequency in the range of Rayleigh numbers from 9.3 x 10³ to 3.5 x 105 and Chandrasekhar numbers 0-1900. The effect of the horizontal magnetic field on the flow pattern may be summarized into three regimes with increases in the magnetic intensity: (1) no effect of the magnetic field, (2) a decrease in the oscillation of the roll structure, and (3) a steady two-dimensional roll structure with no oscillation. These regimes may be explained as a result of an increase in the dominance of Lorentz forces over inertial forces. The power spectrum from the temperature time series showed the presence of a convective-inertial subrange above Rayleigh numbers of 7 x 104, which suggests that turbulence has developed, and such a subrange was commonly observed above this Rayleigh number even with applied magnetic fields when the rolls oscillate.