PB01

Study of DNA triplex formation with two non-pyrimidine-purine-pyrimidine base triads in a Sept-decamer 5’-TTCTTCTGATTCCTCC in Aqueous Solution

 

Min-Tasir Wey and Lou-Sing Kan

Institute of Chemistry, Academia Sinica, Taipei, Taiwan

No.128 Academia Road Section 2, Nan-Kang, Taipei, 11529, Taiwan

 

Triplex formation and stability of sept-decamer 5’-TTCTTCTGATTCCTCC(C) with 5’-GGAGAGAATCAGAAGAA (W) and 5’-CCTCTCTTAGTCTTCTT (H) were studies by UV, CD, surface plasmon resonance, and native gel electrophoresis as a function of pH.  C, W, and H formed CWH triplex at low pH (5) in spite of two non-pyrimidine-purine-pyrimidine (pypupy) base triads in the middle of the oligomer.  This triplex dissociate when pH raising to neutral as a perfect pypupy triplex does. W and C but not H can self-associate into dimers also in an acidic environment by the results of native gel electrophoresis.  The W2     and C2 will dissociate by adding to each other to form CW.  In addition, WH forms by mixing W and H.   However, there is no CH dimer formed.  Thus, the relative affinity of C, H, and W components in triplex CWH were expressed thermodynamically and kinetically in this paper. It is worth to note 5’-TTCTTCTGATTCCTCC is a fragment of cell cycle protein cdc25 gene (696-712) in pneomocystic carinii, a fungi that causes pneumonia in patients with impaired immunity. Thus, our study may aid the discovery of new drug designed against pneomocystic carinii.

 

 

PB02

A Two-photon ,Biomechanical Manipulation Platform for

Tissue Engineering Studies

 

Shu-Wen Teng 1, Chang-Chun Lee 1, Hsiao-Ching Chen 2, Hsuan-Shu Lee 2*, Chen-Yuan Dong 1*

1 Department of Physics ,National Taiwan University,Taiwan and

2 National Taiwan University College of Medicine,Taiwan

No.1, Sec. 4, Roosevelt Road, Taipei, Taiwan 106

 

Tissue engineering is a new and rapidly developing field of biotechnology which aims to grow living and functional tissue for clinical or biotechnological applications. Our research focuses on designing a technological platform for manipulating, imaging, and characterizing tissue-engineered constructs to better understand the growth and differentiation processes. Our system combines bio-reactors, magnetic-tweezers, and two-photon fluorescence microscopy. The bio-reactor is a micro-fluidic chamber biocompatible for cell growth and able to monitor cell differentiation under the influence of growth factors and biomechanical stimuli. Coupled with magnetic-tweezers, the bio-reactor becomes a basis for biomechanical tissue stimulation. Finally, two-photon fluorescence microscopy allows us to obtain high-resolution, in-depth, three-dimensional images of the cultured tissues. We will describe the design of the above platform and discuss its application in tissue engineering studies.

 

 

PB03

Ammonia-induced Structural Changes of the Oxygen-Evolving Complex in Photosystem II as Revealed by Light-Induced FTIR Difference Spectroscopy

 

Ya-Wen Feng, Chiu-Ming Wang and Hsiu-An Chu

Institute of Botany, Academia Sinica, Nan-Kang, Taipei 11529, Taiwan

No.128 Academia Road Section 2, Nan-Kang, Taipei, 11529, Taiwan

 

  The catalytic site of photosystem II (PSII) reaction centers contains a (Mn)4 cluster that interacts closely with a redox-active tyrosine residue known as YZ.  The (Mn)4 cluster accumulates oxidizing equivalents in response to photoinduced electron transfer reactions within PSII, then catalyzes the oxidation of two molecules of water, release one molecule of O2 as a by-product.  The progression of the oxygen-evolving complex (OEC) goes through a cycle of five intermediates states, labeled as the Sn state (n = 0-4), where n denotes the number of stored equivalents.  The detailed molecular structure and mechanism of OEC in PSII are still not clear.  NH3 is an analog of substrate H2O and also an inhibitor of water oxidation.  By combining FTIR difference techniques with isotopic labeling methods, we are studying the interaction of NH3 with the OEC.  We found that the S2 state carboxylate mode in the S2QA-/S1QA spectrum is affected upon the NH3 treatment but the corresponding S1 carboxylate mode at 1402 cm-1 is not affected.  Our results suggest that NH3 is not bound until the formation of the S2 state.  In addition, we found that the other amines did not significantly alter the S2QA-/S1QA FTIR difference spectrum.  Our results suggest that the binding site of NH3 to the OEC is highly specific to ammonia because of steric factors.  In the end, the possible correlations between the NH3-modified FTIR spectra and the NH3-modified g=2 multiline EPR signal will be discussed.