Enhanced strand invasion by peptide nucleic acid-peptide conjugates

Efficient and selective recognition of DNA by proteins is due to sequence-specific interactions with a target site and nonselective electrostatic interactions that promote the target's rapid location. If synthetic molecules could mimic these functions, they would render a wide range of chromosome sequences accessible to rationally designed probes. Here we describe conjugates between bispeptide nucleic acids (bisPNAs) designed to specifically recognize duplex DNA and peptides that have been designed to promote rapid sequence recognition. Peptide design was based on the surface of staphylococcal nuclease, a cationic DNA binding protein with low sequence selectivity. We observe that attachment of the designed peptide increases rates of strand invasion by 100-fold relative to unmodified bisPNA. The peptide can contain D-amino acids, increasing the likelihood that it will be stable in cell extract and inside cells. Binding of the conjugate containing the D-amino acid peptide occurred over a broad range of experimental conditions and was sensitive to a single mismatch. Strand invasion was efficient at neutral to basic pH, a wide range of temperatures (0-65 degrees C), and in the presence of up to 7 mM Mg(2+) and 100 mM Na(+) or K(+). Our data suggest that attachment of peptides that mimic cationic protein surfaces to PNAs can afford conjugates that mimic the rapid and selective binding that characterizes native DNA binding proteins. Rapid strand invasion over a wide range of experimental conditions should further expand the utility of strand invasion by PNAs.     

Reconstruction of the weight-bearing surface of the foot with nonneurosensory free flaps

Neurotized fasciocutaneous flaps and split-skin grafted muscle flaps are the most frequently used free flap alternatives for the reconstruction of weight-bearing surfaces of the foot. An objective comparison of the innate characteristics of these two flap types, with respect to long-term stability, has not been possible because sensory reinnervation in the fasciocutaneous flaps has been a confounding factor. This study compares nonsensate fasciocutaneous flaps (n = 9) with nonsensate split-skin grafted muscle flaps (n = 11), with mean follow-up periods of 34.3 and 31.3 months, respectively. Patients completed a form that included questions regarding degree of pain at the operative site, presence of ulcers, ability to wear normal shoes, employment status, and time spent standing on foot. Touch and deep sensation were evaluated with Semmes-Weinstein and vibration tests, respectively. Significantly less pain and less ulceration (p < 0.05) were observed in the fasciocutaneous group. Semmes-Weinstein monofilament tests revealed poorer results with split-skin grafted muscle flaps, compared with fasciocutaneous flaps. These results indicate that even if the sensory protection of fasciocutaneous flaps is not considered, these flaps have superior properties, compared with split-skin grafted muscle flaps.     

Accumulation of aluminum in rat brain: does it lead to behavioral and electrophysiological changes?

The present study was undertaken to examine possible aluminum (Al) accumulation in the brain of rats and to investigate whether subchronic exposure to the metal leads to behavioral and neurophysiological changes in both treated and control groups. Each of the groups consisted of 10 animals. Aluminum chloride (AlCl₃) at a low (50 mg/kg/d) or high (200 mg/kg/d) dose was applied to male Wistar rats by gavage for 8 wk. Al-free water by gavage was given to the control group throughout the experiment. Behavioral effects were evaluated by open-field (OF) motor activity and by acoustic startle response (ASR). Electrophysiological examination was done by recording spontaneous activity and sensory-evoked potentials from the visual, somatosensory, as well as auditory cortex. The Al content of each whole brain was determined by electrothermal atomic absorption spectrophotometry. Subchronic Al exposure slightly caused some changes in the evoked potentials and electrocorticograms and in the OF and ASR performance, but these results were not statistically significant. The brain Al levels of the control and the low and high dose of Al-exposed groups were measured as 0.717±0.208 μg/g (wet weight), 0.963±0.491 μg/g (wet weight) and 1.816±1.157 μg/g (wet weight), respectively.