KEIO RESEARCHERS INFORMATION SYSTEM

Academic Background 【 Display / hide 】

Academic Background 【 Display / hide 】

• 2007.10

  -

  2011.02

  University of Belgrade, Serbia, Mechanical Engineering, Department of Automatic Control, Biomedical Engineering

  Serbia, Graduate School, Graduated, Doctoral course

Research Areas 【 Display / hide 】

Research Areas 【 Display / hide 】

• Natural Science / Biophysics, chemical physics and soft matter physics

Research Keywords 【 Display / hide 】

Research Keywords 【 Display / hide 】

• Water, hydrogen bonding, near-infrared spectroscopy, chemometrics, image processing.

Research Themes 【 Display / hide 】

Research Themes 【 Display / hide 】

• Aquaphotomics: water-as-a-mirror approach to studying role of water in biological systems., 

  2011.03

  -

  2017.04

  　View Summary

  Diagnosing disease from urine using water-as-a-mirror application to near-infrared spectroscopy.
  Resolving the interaction between water and various biomolecules. Fingerprinting hydrophilic and hydrophobic solutes.
  Exploration of van der Waals forces in water.

Books 【 Display / hide 】

Books 【 Display / hide 】

• Biomedical Science, Engineering and Technology

  D. Kojic, B. Bojovic, Stamenkovic D., Jagodic N., Dj. Koruga, InTech, Croatia, 2011

  Scope: Chapter 15: Contact Lenses Characterization by Atomic Force Microscopy, Magnetic Force Microscopy, and OptoMagnetic Fingerprint

• Introduction to nanotechnologies

  Kojic Dusan, Science, Belgrade, Serbia (in Serbian), 2009.01

Papers 【 Display / hide 】

Papers 【 Display / hide 】

• Improving accuracy and reproducibility of vibrational spectra for diluted solutions

  Kojic Dusan,Roumiana Tsenkova,Masato Yasui

  Analytica Chimica Acta (Elsevier)  955   86 - 97 2017.02

  Joint Work, Accepted,  ISSN  0003-2670

  • Access to Document (DOI)

• Velocity auto-correlation function of ions and water molecules in different concentrations, anions, and ion clusters

  Katsufumi Tomobe, Eiji Yamamoto, Dusan Kojic, Masato Yasui, Kenji Yasuoka

  Molecular Simulation (Taylor & Francis Online)  41 ( 10-12 ) 840 - 844 2015

  Research paper (other academic), Joint Work

  　View Summary

  The characteristics of ion solvation are important for electrochemical and biophysical phenomena because all such phenomena occur under the presence of solvated ions. In this study, we performed an all-atom molecular dynamics simulation of aqueous NaCl ranging from 0.5 to 3.0 M, and aqueous NaF, NaBr and NaI in 2.0 M, to investigate the time-averaged velocity auto-correlation function (TAVAF) of ions and water molecules. By comparing the concentrations and ion pairs, we observed three behaviours: (i) in the case of NaCl, the velocity auto-correlation of Cl− becomes weaker as the concentration increases, whereas those of Na+ are not clearly different, (ii) the intensity of fluctuations of the TAVAF gradually decreases following the decrease in ionic radius and (iii) every TAVAF of water molecules in ionic solutions is clearly lower than that of bulk because of the cage effect. Furthermore, we observed that the first minimum of the TAVAF in the cluster is smaller than that of the isolated ions. These results indicate that the diffusion of ions and water molecules is affected by cage effect, and that the generation of ion cluster affects the diffusion of ions.

  • Access to Document (DOI)

• Water confined in the local field of ions

  Kojic D., Tsenkova R., Tomobe K., Yasuoka K., Yasui M.

  European Journal of Chemical Physics and Physical Chemistry (Wiley Online)  15 ( 18 ) 4077 - 4086 2014.12

  Research paper (other academic), Joint Work,  ISSN  1439-7641

  　View Summary

  Interionic distances are shorter in concentrated ionic solutions, thus instigating the interaction and overlap of hydration shells, as ions become separated by only one or two layers of water molecules. The simultaneous interaction of water with two oppositely charged ions has, so far, only been investigated by computer simulation studies, because the isolated vibrational spectroscopic signature of these molecules remains undetected. Our combined near-infrared spectroscopic and molecular dynamics simulation studies of alkali halide solutions present a distinct spectral feature, which is highly responsive to depletion of bulk water and merging of hydration shells. The analysis of this spectral feature demonstrates that absorption trends are in good agreement with the law of matching affinities, thus providing the first successful vibrational spectroscopic treatment of this topic. Combined with commonly observed near-infrared bands, this feature provides a spectral pattern that describes some relevant aspects of ionic hydration.

  • Access to Document (DOI)

• Unprecedented Cell-Selection Using Ultra-Quick Freezing Combined with Aquaporin Expression

  Kato Y., Miyauchi T., Abe Y., Kojic D., Tanaka M., Chikazawa N., Nakatake Y., Ko S., Kobayashi D., Hazama A., Fujiwara S., Uchida T., Yasui M.

  PLOS ONE (PLOS)  9 ( 2 ) e87644 2014.02

  Research paper (other academic), Joint Work,  ISSN  1932-6203

  　View Summary

  Freezing is usually used for preservation and storage of biological samples; however, this process may have some adverse effects such as cell membrane damage. Aquaporin (AQP), a water channel protein, has been suggested to play some roles for cryopreservation although its molecular mechanism remains unclear. Here we show that membrane damage caused by ultra-quick freezing is rescued by the expression of AQP4. We next examine if the expression of AQP combined with ultra-quick freezing can be used to select cells efficiently under freezing conditions where most cells are died. CHO cells stably expressing AQP4 were exclusively selected from mixed cell cultures. Having identified the increased expression of AQP4 during ES cell differentiation into neuro-ectoderm using bioinformatics, we confirmed the improved survival of differentiated ES cells with AQP4 expression. Finally we show that CHO cells transiently transfected with Endothelin receptor A and Aqp4 were also selected and concentrated by multiple cycles of freezing/thawing, which was confirmed with calcium imaging in response to endothelin. Furthermore, we found that the expression of AQP enables a reduction in the amount of cryoprotectants for freezing, thereby decreasing osmotic stress and cellular toxicity. Taken together, we propose that this simple but efficient and safe method may be applicable to the selection of mammalian cells for applications in regenerative medicine as well as cell-based functional assays or drug screening protocols.

  • Access to Document (DOI)

• Magnetic properties of Co1+yAl2-yO4–SiO2 nanocomposites synthesized by sol-gel method

  D. Milivojevic, B. Babic-Stojic, V. Jokanovic, Z. Jaglicic, D. Brankovic, N. Jovic, S. Cupic, D. Kojic

  Journal of Sol-Gel Science and Technology (Springer Link)  63 ( 1 ) 56 - 64 2012

  Research paper (other academic), Joint Work,  ISSN  1573-4846

  　View Summary

  Nanocomposites made of magnetic spinel oxide Co1+yAl2−yO4 particles dispersed in an amorphous SiO2 matrix were synthesized by a sol–gel technique. Samples with various mass fractions of Co1+yAl2−yO4 in composite x, and with various Co concentrations in spinel y were studied. The grain sizes were below 100 nm with a large size distribution. The paper represents thorough investigation of magnetic properties, but special attention was given to peculiar effects and low temperature magnetic frozen states. Magnetic measurements reveal multiple magnetic ground states at the lowest temperature. The frequency dependent ac susceptibility measurements indicate spin-glass behavior of these ground states at low temperatures. The samples, with higher concentration x of Co1+yAl2−yO4 in SiO2, showed very similar Curie–Weiss paramagnetic behavior with antiferromagnetically interacting Co ions (θ ≈ −100 K). Other samples, with lower x, showed complex behavior, spin-glass magnetic freezing at the lowest temperatures and lower absolute value of θ and consequently lower exchange constant.

  • Access to Document (DOI)

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