In this article, we report on the heat-transfer resistance at interfaces as a novel, denaturation-based method to detect single-nucleotide polymorphisms in DNA. We observed that a molecular brush of double-stranded DNA grafted onto synthetic diamond surfaces does not notably affect the heat-transfer resistance at the solid-to-liquid interface. In contrast to this, molecular brushes of single-stranded DNA cause, surprisingly, a substantially higher heat-transfer resistance and behave like a thermally insulating layer. This effect can be utilized to identify ds-DNA melting temperatures via the switching from low- to high heat-transfer resistance. The melting temperatures identified with this method for different DNA duplexes (29 base pairs without and with built-in mutations) correlate nicely with data calculated by modeling. The method is fast, label-free (without the need for fluorescent or radioactive markers), allows for repetitive measurements, and can also be extended toward array formats. Reference measurements by confocal fluorescence microscopy and impedance spectroscopy confirm that the switching of heat-transfer resistance upon denaturation is indeed related to the thermal on-chip denaturation of DNA.

No abstract

No abstract

No abstract

We report on the use of the heat transfer method, a novel surface‐sensitive technique based on heat transfer through solid–liquid interfaces, to detect phase transitions of model lipid membranes. We selected the lipid DPPC because of its rich phase behavior in an experimentally accessible temperature range. The vesicles were adsorbed on nanocrystalline diamond films, known as a versatile platform material for biosensing with outstanding heat‐conduction properties. Complementary Peltier‐element‐based adiabatic scanning calorimetry (pASC) and quartz crystal microbalance with dissipation monitoring (QCM‐D) measurements were carried out to monitor the phase transitions in multilamellar and small unilamellar vesicles, respectively. The heat‐transfer measurements revealed reversible jumps upon heating and cooling in the thermal resistance in the vicinity of the expected transition temperature and they agree qualitatively with molecular simulations of the thermal conductivity across a lipid bilayer. The results show the capability of the heat transfer method to detect the main phase transition in DPPC, opening new perspectives for the study of more complex lipid systems and different solid platforms. This work confirms QCM‐D as a useful tool for the assessment of the structural changes upon the phase conversion and shows the capability of pASC to provide high‐resolution thermodynamic information on biophysical systems. Temperature profile of the heat transfer resistance Rth during the main phase transition of a DPPC supported vesicle layer adsorbed on a hydrogen‐terminated nanocrystalline diamond substrate. The arrows indicate the sense of the run: heating (red solid line) and cooling (blue solid line).

In this article, we report on the electronic monitoring of DNA denaturation by NaOH using electrochemical impedance spectroscopy in combination with fluorescence imaging as a reference technique. The probe DNA consisting of a 36-mer fragment was covalently immobilized on nanocrystalline-diamond electrodes and hybridized with different types of 29-mer target DNA (complementary, single-nucleotide defects at two different positions, and a non-complementary random sequence). The mathematical separation of the impedimetric signals into the time constant for NaOH exposure and the intrinsic denaturation-time constants gives clear evidence that the denaturation times reflect the intrinsic stability of the DNA duplexes. The intrinsic time constants correlate with calculated DNA-melting temperatures. The impedimetric method requires minimal instrumentation, is label-free and fast with a typical time scale of minutes and is highly reproducible. The sensor electrodes can be used repetitively. These elements suggest that the monitoring of chemically induced denaturation at room temperature is an interesting approach to measure DNA duplex stability as an alternative to thermal denaturation at elevated temperatures, used in DNA-melting experiments and single nucleotide polymorphism (SNP) analysis.

Exchange-coupled dopants in Si quantum dots Appl. Phys. Lett. 101, 093108 (2012) Understanding the distribution of iron in multicrystalline silicon after emitter formation: Theoretical model and experiments J. Appl. Phys. 109, 063717 (2011) Atomic scale evidence of the suppression of boron clustering in implanted silicon by carbon coimplantation J. Appl. Phys. 109, 023501 (2011) Combined light and electron scattering for exploring hydrogen in thin metallic films Appl. Phys. Lett. 97, 251910 (2010) Diluted manganese on the bond-centered site in germanium Appl. Phys. Lett. 97, 151914 (2010) Additional information on Appl. Phys. Lett.

No abstract