Dynamic force spectroscopy of single DNA molecules

To explore the analytic relevance of unbinding force measurements between complementary DNA strands with an atomic force microscope, we measured the forces to mechanically separate a single DNA duplex under physiological conditions by pulling at the opposite 5'-ends as a function of the loading rate (dynamic force spectroscopy). We investigated DNA duplexes with 10, 20, and 30 base pairs with loading rates in the range of 16-4,000 pN/s. Depending on the loading rate and sequence length, the unbinding forces of single duplexes varied from 20 to 50 pN. These unbinding forces are found to scale with the logarithm of the loading rate, which is interpreted in terms of a single energy barrier along the mechanical separation path. The parameters describing the energy landscape, i.e. , the distance of the energy barrier to the minimum energy along the separation path and the logarithm of the thermal dissociation rate, are found to be proportional to the number of base pairs of the DNA duplex. These single molecule results allow a quantitative comparison with data from thermodynamic ensemble measurements and a discussion of the analytic applications of unbinding force measurements for DNA.     

Changes in hippocampal volume during a preceding 10-year period do not correlate with cognitive performance and hippocampal blood‒brain barrier permeability in cognitively normal late-middle-aged men

GeroScience - Hippocampal blood–brain barrier (BBB) permeability may increase in normal healthy ageing and contribute to neurodegenerative disease. To examine this hypothesis, we investigated...     

Prevalence of Sjögren's syndrome in patients with dry mouth in the region of Central Hungary

Objective

One-third of the Hungarian population suffers from xerostomia. Since there is no evidence of the actual prevalence of Sjögren's syndrome (SS) in Hungary, this study aimed to evaluate the same.

Materials and Methods

Data were collected from the Faculty of Dentistry, Semmelweis University from 2008 to 2015. A diagnosis of SS was established based on the American College of Rheumatology and European League Against Rheumatism criteria.

Results

Of the 1076 patients examined with sicca symptoms, 188 patients had confirmed SS. Primary SS (pSS) was diagnosed in 135 patients and secondary SS (sSS) was confirmed in 53 patients. According to the available statistical records of the public health service of Hungary, there were an average of 16 (0.0014%, 5–26) newly diagnosed SS cases in the entire population and 141 SS patient-practitioner consultations (49–232) per 100,000 inhabitants in the country over the past 10 years (based on the past 10 years: 2011–2020).

Conclusion

Results revealed that approximately 1/5th–1/6th of patients with sicca symptoms have SS, among whom 72% and 285 have pSS and sSS, respectively. Global Hungarian records simultaneously revealed that the number of both new diagnoses and doctor-SS patient encounters has significantly decreased (by 50%) yearly over the last decade.