Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Article Citation - WoS: 2Citation - Scopus: 2Morphology of Sodium Salt of Calf Thymus Dna on Mica, Alumina, and Silica Surfaces: Effect of Solvent and Drying Method(Taylor and Francis Ltd., 2017) Yetgin, Senem; Balköse, DevrimInvestigation of morphology of deoxyribonucleotide triphosphate (DNA) dried on different surfaces by atomic force microscopy (AFM) is important in DNA research that is focused on subjects of condensation for gene therapy, sizing, DNA mapping, and cancer examination. The solvent, the surface type, and the method of drying effect the morphology of DNA on solid surfaces. Ethanol and water were used as solvents, flat mica, silica, and alumina surfaces were used as the substrates in the present study. Different methods such as ambient air-drying, N2-forced flow regime drying, and freeze-drying have been applied to droplets of DNA solutions in water or ethanol on the substrates. Forced flow drying regime causes nonlinear DNA attachment on the surface and self-assembly. DNA vertical distance on mica surface was found to be 6 and 1.4 nm for DNA dried in ambient air from ethanol and water solutions, respectively. It was 1.6 nm for N2 flow drying of aqueous DNA solution on mica surface. It was 4.6, 4.6, and 1.99 nm for ambient, N2 flow, and freeze-dried aqueous DNA on alumina surfaces, respectively. Aqueous solution of DNA dried under N2 flow on silica surface had 0.8 nm vertical distance. The smallest standard deviation of 0.05 nm was observed for DNA dried under N2 flow on alumina surface.Article Citation - WoS: 19Citation - Scopus: 23Influence of Microstructure on the Rheological Behavior of Dense Particle Gels(John Wiley and Sons Inc., 2005) Wyss, Hans M.; Deliormanlı, Aylin M.; Tervoort, Elena V.; Gauckler, Ludwig JuliusRheological measurements are performed on highly concentrated alumina gels. By using an in situ mechanism based on enzyme-catalyzed internal reactions, we are able to form gels of highly concentrated particles without disturbing the microstructures that develop during the gelation process. These gels are produced by two different destabilization mechanisms: Either the pH of the suspension is shifted toward the isoelectric point (ΔpH method) or the ionic strength of the suspension is increased at a constant pH (ΔI method). The two destabilization mechanisms lead to gels of significantly different microstructures. We find notable differences in the rheological behavior of the two systems, suggesting a bond-bending mechanism for stress transmission in the case of ΔpH gels and a bond-stretching mechanism in the case of ΔI gels. In addition, for both kinds of gels we compare the in situ properties to those obtained after altering the microstructure by shearing. Results suggest an increase in elastic and yield properties of concentrated particle gels with decreasing homogeneity of their microstructures.