Browsing by Issue Date, starting with "2011-09-05"

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交大e-News第101期
(2011-09-05)
Secretariat
;
國立交通大學秘書室
Microwave-Assisted Tandem Transformation on an Ionic-Liquid Support: Efficient Synthesis of Pyrrolo/Pyridobenzimidazolones and Isoindolinone-Fused Benzimidazoles
(2011-09-05)
Thummanagoti, Suman
;
Yellol, Gorakh S.
;
Sun, Chung-Ming
;
應用化學系
;
Department of Applied Chemistry
A tandem transformation that involves the formation of three bonds and two heterocyclic rings in a one-pot fashion through amino-alkylation of an ionic-liquid-immobilized diamine with keto acids followed by successive double intramolecular cyclizations to afford a tricyclic framework has been explored. This tandem cyclization has been utilized to develop a rapid and efficient method to synthesize various pyrrolo[1,2-a]benzimidazolones and pyrido[1,2-a]benzimidazolones on an ionic-liquid support by using focused microwave irradiation. The application of this tandem cyclization was further extended to the aromatic keto acids to provide isoindolinone-fused benzimidazoles, a structurally heterogeneous library with skeletal diversity. The outcome of the cascade reaction was confirmed by the X-ray crystallographic study of the product directly attached to the ionic-liquid support. Use of the ionic liquid as a soluble support facilitates purification by simple precipitation along with advantages like high loading capacity, homogeneous reaction conditions, and monitoring of the reaction progress by regular conventional spectroscopic methods, whereas application of microwave irradiation greatly accelerates the rate of the reactions.
Comparative study of cluster Ag(17)Cu(2) by instantaneous normal mode analysis and by isothermal Brownian-type molecular dynamics simulation
(2011-09-07)
Tang, Ping-Han
;
Wu, Ten-Ming
;
Yen, Tsung-Wen
;
Lai, S. K.
;
Hsu, P. J.
We perform isothermal Brownian-type molecular dynamics simulations to obtain the velocity auto-correlation function and its time Fourier-transformed power spectral density for the metallic cluster Ag(17)Cu(2). The temperature dependences of these dynamical quantities from T = 0 to 1500 K were examined and across this temperature range the cluster melting temperature T(m), which we define to be the principal maximum position of the specific heat is determined. The instantaneous normal mode analysis is then used to dissect the cluster dynamics by calculating the vibrational instantaneous normal mode density of states and hence its frequency integrated value I(j) which is an ensemble average of all vibrational projection operators for the jth atom in the cluster. In addition to comparing the results with simulation data, we look more closely at the entities I(j) of all atoms using the point group symmetry and diagnose their temperature variations. We find that I(j) exhibit features that may be used to deduce T(m), which turns out to agree very well with those inferred from the power spectral density and specific heat. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3628669]
Comparative study of cluster Ag17Cu2 by instantaneous normal mode analysis and by isothermal Brownian-type molecular dynamics simulation
(2011-09-07)
Tang, Ping-Han
;
Wu, Ten-Ming
;
Yen, Tsung-Wen
;
Lai, S. K.
;
Hsu, P. J.
We perform isothermal Brownian-type molecular dynamics simulations to obtain the velocity auto-correlation function and its time Fourier-transformed power spectral density for the metallic cluster Ag17Cu2. The temperature dependences of these dynamical quantities from T = 0 to 1500 K were examined and across this temperature range the cluster melting temperature T-m, which we define to be the principal maximum position of the specific heat is determined. The instantaneous normal mode analysis is then used to dissect the cluster dynamics by calculating the vibrational instantaneous normal mode density of states and hence its frequency integrated value I-j which is an ensemble average of all vibrational projection operators for the jth atom in the cluster. In addition to comparing the results with simulation data, we look more closely at the entities I-j of all atoms using the point group symmetry and diagnose their temperature variations. We find that I-j exhibit features that may be used to deduce T-m, which turns out to agree very well with those inferred from the power spectral density and specific heat. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3628669]
Pressure dependence of the electronic structure and spin state in Fe(1.01)Se superconductors probed by x-ray absorption and x-ray emission spectroscopy
(2011-09-09)
Chen, J. M.
;
Haw, S. C.
;
Lee, J. M.
;
Chou, T. L.
;
Chen, S. A.
Pressure dependence of electronic structures and spin states of iron-chalcogenide Fe(1.01)Se superconductors up to similar to 66 GPa has been investigated with x-ray emission spectra and x-ray absorption spectra with partial-fluorescence yield. The intensity of the pre-edge peak at energy of similar to 7112.7 eV of the Fe K-edge x-ray absorption spectrum of Fe1.01Se decreases progressively with pressure up to similar to 10 GPa. A new prepeak at energy of similar to 7113.7 eV develops for pressure above similar to 13 GPa, indicating formation of a new phase. The experimental and the calculated Fe K-edge absorption spectra of Fe(1.01)Se using the FDMNES code agree satisfactorily. The larger compression accompanied by significant distortion around the Fe atoms along the c axis in Fe(1.01)Se upon applying pressure suppresses the Fe 3d-Se 4p and Fe 4p-Se 4d hybridization. The applied pressure suppresses the nearest-neighbor ferromagnetic superexchange interaction and enhances spin fluctuations on the Fe sites in Fe(1.01)Se. A discontinuous variation of the integrated absolute difference values of the K beta emission line was observed, originating from a phase transition of Fe(1.01)Se for a pressure >12 GPa. Fe(1.01)Se shows a small net magnetic moment of Fe(2 broken vertical bar) at ambient pressure, probably arising from strong Fe-Fe spin fluctuations. The satellite line K beta' was reduced in intensity upon applying pressure and became absent for pressure >52 GPa, indicating a continuous reduction of the spin moment of Fe in Fe(1.01)Se superconductors. The experimental results provide insight into the spin state of Fe(1.01)Se superconductors under pressure.
Minimal Antizyme Peptide Fully Functioning in the Binding and Inhibition of Ornithine Decarboxylase and Antizyme Inhibitor
(2011-09-09)
Hsieh, Ju-Yi
;
Yang, Jung-Yen
;
Lin, Chih-Li
;
Liu, Guang-Yaw
;
Hung, Hui-Chih
Antizyme (AZ) is a protein with 228 amino acid residues that regulates ornithine decarboxylase (ODC) by binding to ODC and dissociating its homodimer, thus inhibiting its enzyme activity. Antizyme inhibitor (AZI) is homologous to ODC, but has a higher affinity than ODC for AZ. In this study, we quantified the biomolecular interactions between AZ and ODC as well as AZ and AZI to identify functional AZ peptides that could bind to ODC and AZI and inhibit their function as efficiently as the full-length AZ protein. For these AZ peptides, the inhibitory ability of AZ_95-228 was similar to that of AZ_WT. Furthermore, AZ_95-176 displayed an inhibition (IC(50): 0.20 mu M) similar to that of AZ-95-228 (IC(50): 0.16 mM), even though a large segment spanning residues 177-228 was deleted. However, further deletion of AZ_95-176 from either the N-terminus or the C-terminus decreased its ability to inhibit ODC. The AZ_100-176 and AZ_95-169 peptides displayed a noteworthy decrease in ability to inhibit ODC, with IC(50) values of 0.43 and 0.37 mM, respectively. The AZ_95-228, AZ_100-228 and AZ_95-176 peptides had IC(50) values comparable to that of AZ_WT and formed AZ-ODC complexes with K(d,AZ-ODC) values of 1.5, 5.3 and 5.6 mu M, respectively. Importantly, our data also indicate that AZI can rescue AZ peptide-inhibited ODC enzyme activity and that it can bind to AZ peptides with a higher affinity than ODC. Together, these data suggest that these truncated AZ proteins retain their AZI-binding ability. Thus, we suggest that AZ_ 95-176 is the minimal AZ peptide that is fully functioning in the binding of ODC and AZI and inhibition of their function.
Pressure dependence of the electronic structure and spin state in Fe1.01Se superconductors probed by x-ray absorption and x-ray emission spectroscopy
(2011-09-09)
Chen, J. M.
;
Haw, S. C.
;
Lee, J. M.
;
Chou, T. L.
;
Chen, S. A.
Pressure dependence of electronic structures and spin states of iron-chalcogenide Fe1.01Se superconductors up to similar to 66 GPa has been investigated with x-ray emission spectra and x-ray absorption spectra with partial-fluorescence yield. The intensity of the pre-edge peak at energy of similar to 7112.7 eV of the Fe K-edge x-ray absorption spectrum of Fe1.01Se decreases progressively with pressure up to similar to 10 GPa. A new prepeak at energy of similar to 7113.7 eV develops for pressure above similar to 13 GPa, indicating formation of a new phase. The experimental and the calculated Fe K-edge absorption spectra of Fe1.01Se using the FDMNES code agree satisfactorily. The larger compression accompanied by significant distortion around the Fe atoms along the c axis in Fe1.01Se upon applying pressure suppresses the Fe 3d-Se 4p and Fe 4p-Se 4d hybridization. The applied pressure suppresses the nearest-neighbor ferromagnetic superexchange interaction and enhances spin fluctuations on the Fe sites in Fe1.01Se. A discontinuous variation of the integrated absolute difference values of the K beta emission line was observed, originating from a phase transition of Fe1.01Se for a pressure >12 GPa. Fe1.01Se shows a small net magnetic moment of Fe-2 broken vertical bar at ambient pressure, probably arising from strong Fe-Fe spin fluctuations. The satellite line K beta' was reduced in intensity upon applying pressure and became absent for pressure >52 GPa, indicating a continuous reduction of the spin moment of Fe in Fe1.01Se superconductors. The experimental results provide insight into the spin state of Fe1.01Se superconductors under pressure.
三維微探針陣列的組裝結構
(2011-09-11)
邱俊誠
;
張志瑋
一種三維微探針陣列的組裝結構，利用墊片(spacer)的概念，疊加單片側向式探針成為三維立體結構，並且使每一片側向式探針之導電片皆於墊片露出，使得導線易於連接，而可同時偵測深度與角度，有效的增進感測可靠度，此外，亦可將相關訊號處理積體電路與墊片整合，更可達到整合電路與降低製造成本的優勢。
Enhanced efficiency for c-Si solar cell with nanopillar array via quantum dots layers
(2011-09-12)
Chen, Hsin-Chu
;
Lin, Chien-Chung
;
Han, Hao-Wei
;
Tsai, Yu-Lin
;
Chang, Chia-Hua
The enhanced efficiency of the crystalline silicon (c-Si) solar cell with nanopillar arrays (NPAs) was demonstrated by deployment of CdS quantum dots (QDs). The NPAs was fabricated by the colloidal lithography and reactive-ion etching techniques. Under a simulated one-sun condition, the device with CdS QDs shows a 33% improvement of power conversion efficiency, compared with the one without QDs. For further investigation, the excitation spectrum of photoluminescence (PL), absorbance spectrum, current-voltage (I-V) characteristics, reflectance and external quantum efficiency of the device was measured and analyzed. It is noteworthy that the enhancement of efficiency could be attributed to the photon down-conversion, the antireflection, and the improved electrical property. (C) 2011 Optical Society of America
Lasing at exciton transition in optically pumped gallium nitride nanopillars
(2011-09-12)
Lo, Ming-Hua
;
Cheng, Yuh-Jen
;
Liu, Mei-Chun
;
Kuo, Hao-Chung
;
Wang, Shing Chung
We report the observation of room temperature lasing action in optically pumped GaN nanopillars. The nanopillars were fabricated by patterned etching and crystalline regrowth from a GaN substrate. When nanopillars were optically excited, a narrow emission peak emerged from the broad spontaneous emission background. The increasing rate is nine times faster than that of the spontaneous emission background, showing the onset of lasing action. The lasing occurs right at the center of spontaneous emission rather than the often reported redshifted wavelength. A spectroscopic ellipsometry analysis indicates that the gain of lasing action is provided by exciton transition. (C) 2011 Optical Society of America
Di(4-methylphenyl)methano-C-60 Bis-Adduct for Efficient and Stable Organic Photovoltaics with Enhanced Open-Circuit Voltage
(2011-09-13)
Cheng, Yen-Ju
;
Liao, Ming-Hung
;
Chang, Chih-Yu
;
Kao, Wei-Shun
;
Wu, Cheng-En
A new class of fullerene bis-adducts di(4-methyl-phenyl)methano-C-60 bis-adduct (DMPCBA), di(4-fluorophenyl)methano-C-60 bis-adduct (DFPCBA), and diphenylmethano-C-60 bis-adduct (DPCBA) were rationally designed and easily synthesized. Compared to the lowest unoccupied molecular orbital (LUMO) energy level of PC61BM (-3.95 eV), the double functionalization effectively raises the LUMO energy levels of these fullerene materials to ca. -3.85 eV, regardless of the substituent groups (CH3-, F-, and H-) at the para-position of the phenyl rings. This phenomenon suggests that the plane of the phenyl groups is preferentially parallel to the fullerene surface, leading to poor orbital interactions with C-60 and negligible electronic effect. Importantly, such geometry sterically protects and shields the core C-60 structure from severe intermolecular aggregation, rendering it intrinsically soluble, morphologically amorphous, and thermally stable. The device based on the P3HT:DMPCBA blend exhibited an open-circuit voltage (V-oc) of 0.87 V, a short-circuit current density (J(sc)) of 9.05 mA/cm(2), and a fill factor (FF) of 65.5%, leading to a high power conversion efficiency (PCE) of 5.2%, which is superior to that of the P3HT:PC61BM-based device. Most significantly, the amorphous nature of DMPCBA effectively suppresses the thermal-driven aggregation and thus stabilizes the morphology of the P3HT:DMPCBA blend. Consequently, the device retained 80% of its original PCE value against thermal heating at 160 degrees C over 20 h.
Manufacturing multilayer conjugate polymer optoelectronics device by using buffer layer
(2011-09-13)
Meng Hsin-Fei
;
Horng Sheng-Fu
;
Hsu Chain-Shu
;
Lin Shi-Cheng
;
Liao Hua-Hsien
A highly stable, multilayer organic molecular photoelectric element without interlayer miscibility phenomenon during manufacturing process, and a method for producing multilayer organic molecular photoelectric elements with simplified solution process are disclosed.
Di(4-methylphenyl)methano-C(60) Bis-Adduct for Efficient and Stable Organic Photovoltaics with Enhanced Open-Circuit Voltage
(2011-09-13)
Cheng, Yen-Ju
;
Liao, Ming-Hung
;
Chang, Chih-Yu
;
Kao, Wei-Shun
;
Wu, Cheng-En
A new class of fullerene bis-adducts di(4-methyl-phenyl)methano-C(60) bis-adduct (DMPCBA), di(4-fluorophenyl)methano-C(60) bis-adduct (DFPCBA), and diphenylmethano-C(60) bis-adduct (DPCBA) were rationally designed and easily synthesized. Compared to the lowest unoccupied molecular orbital (LUMO) energy level of PC(61)BM (-3.95 eV), the double functionalization effectively raises the LUMO energy levels of these fullerene materials to ca. -3.85 eV, regardless of the substituent groups (CH(3)-, F-, and H-) at the para-position of the phenyl rings. This phenomenon suggests that the plane of the phenyl groups is preferentially parallel to the fullerene surface, leading to poor orbital interactions with C(60) and negligible electronic effect. Importantly, such geometry sterically protects and shields the core C(60) structure from severe intermolecular aggregation, rendering it intrinsically soluble, morphologically amorphous, and thermally stable. The device based on the P3HT:DMPCBA blend exhibited an open-circuit voltage (V(oc)) of 0.87 V, a short-circuit current density (J(sc)) of 9.05 mA/cm(2), and a fill factor (FF) of 65.5%, leading to a high power conversion efficiency (PCE) of 5.2%, which is superior to that of the P3HT:PC(61)BM-based device. Most significantly, the amorphous nature of DMPCBA effectively suppresses the thermal-driven aggregation and thus stabilizes the morphology of the P3HT:DMPCBA blend. Consequently, the device retained 80% of its original PCE value against thermal heating at 160 degrees C over 20 h.
The visible spectrum of zirconium dioxide, ZrO(2)
(2011-09-14)
Le, Anh
;
Steimle, Timothy C.
;
Gupta, Varun
;
Rice, Corey A.
;
Maier, John P.
The electronic spectrum of a cold molecular beam of zirconium dioxide, ZrO(2), has been investigated using laser induced fluorescence (LW) in the region from 17 000 cm(-1) to 18 800 cm(-1) and by mass-resolved resonance enhanced multi-photon ionization (REMPI) spectroscopy from 17 000 cm(-1)-21 000 cm(-1). The LIF and REMPI spectra are assigned to progressions in the (A) over tilde (1) B(2)(v(1), v(2), v(3)) <- (X) over tilde (1) A(1)(0, 0, 0) transitions. Dispersed fluorescence from 13 bands was recorded and analyzed to produce harmonic vibrational parameters for the (X) over tilde (1) A(1) state of omega(1) = 898(1) cm(-1), omega(2) = 287(2) cm(-1), and omega(3) = 808(3) cm(-1). The observed transition frequencies of 45 bands in the LIF and REMPI spectra produce origin and harmonic vibrational parameters for the (A) over tilde (1) B(2) state of T(e) = 16 307(8) cm(-1), omega(1) = 819(3) cm(-1), omega(2) = 149(3) cm(-1), and omega(3) = 518(4) cm(-1). The spectra were modeled using a normal coordinate analysis and Franck-Condon factor predictions. The structures, harmonic vibrational frequencies, and the potential energies as a function of bending angle for the (A) over tilde (1) B(2) and (X) over tilde (1) A(1) states are predicted using time-dependent density functional theory, complete active space self-consistent field, and related first-principle calculations. A comparison with isovalent TiO(2) is made. (C) 2011 American Institute of Physics. [doi:10.1063/1.3632053]
The visible spectrum of zirconium dioxide, ZrO2
(2011-09-14)
Le, Anh
;
Steimle, Timothy C.
;
Gupta, Varun
;
Rice, Corey A.
;
Maier, John P.
The electronic spectrum of a cold molecular beam of zirconium dioxide, ZrO2, has been investigated using laser induced fluorescence (LW) in the region from 17 000 cm(-1) to 18 800 cm(-1) and by mass-resolved resonance enhanced multi-photon ionization (REMPI) spectroscopy from 17 000 cm(-1)-21 000 cm(-1). The LIF and REMPI spectra are assigned to progressions in the (A) over tilde (1) B-2(v(1), v(2), v(3)) <- (X) over tilde (1) A(1)(0, 0, 0) transitions. Dispersed fluorescence from 13 bands was recorded and analyzed to produce harmonic vibrational parameters for the (X) over tilde (1) A(1) state of omega(1) = 898(1) cm(-1), omega(2) = 287(2) cm(-1), and omega(3) = 808(3) cm(-1). The observed transition frequencies of 45 bands in the LIF and REMPI spectra produce origin and harmonic vibrational parameters for the (A) over tilde (1) B-2 state of T-e = 16 307(8) cm(-1), omega(1) = 819(3) cm(-1), omega(2) = 149(3) cm(-1), and omega(3) = 518(4) cm(-1). The spectra were modeled using a normal coordinate analysis and Franck-Condon factor predictions. The structures, harmonic vibrational frequencies, and the potential energies as a function of bending angle for the (A) over tilde (1) B-2 and (X) over tilde (1) A(1) states are predicted using time-dependent density functional theory, complete active space self-consistent field, and related first-principle calculations. A comparison with isovalent TiO2 is made. (C) 2011 American Institute of Physics. [doi:10.1063/1.3632053]
Numerical ranges of weighted shifts
(2011-09-15)
Wang, Kuo-Zhong
;
Wu, Pei Yuan
;
應用數學系
;
Department of Applied Mathematics
Let A be a unilateral (resp., bilateral) weighted shift with weights w(n), n >= 0 (resp., -infinity < n < infinity). Eckstein and Racz showed before that A has its numerical range W (A) contained in the closed unit disc if and only if there is a sequence {a(n)}(n=0)(infinity) (resp., {a(n))(n=-infinity)(infinity)) in [-1,1] such that |w(n)|(2) = (1 - a(n))(1 + a(n+1)) for all n. In terms of such a(n)'s, we obtain a necessary and sufficient condition for W (A) to be open. If the w(n)'s are periodic, we show that the a(n)'s can also be chosen to be periodic. As a result, we give an alternative proof for the openness of W (A) for an A with periodic weights, which was first proven by Stout. More generally, a conjecture of his on the openness of W (A) for A with split periodic weights is also confirmed. (C) 2011 Elsevier Inc. All rights reserved.
Social trend tracking by time series based social tagging clustering
(2011-09-15)
Chen, Shihn-Yuarn
;
Tseng, Tzu-Ting
;
Ke, Hao-Ren
;
Sun, Chuen-Tsai
;
資訊工程學系
Social tagging is widely practiced in the Web 2.0 era. Users can annotate useful or interesting Web resources with keywords for future reference. Social tagging also facilitates sharing of Web resources. This study reviews the chronological variation of social tagging data and tracks social trends by clustering tag time series. The data corpus in this study is collected from Hemidemi.com. A tag is represented in a time series form according to its annotating Web pages. Then time series clustering is applied to group tag time series with similar patterns and trends in the same time period. Finally, the similarities between clusters in different time periods are calculated to determine which clusters have similar themes, and the trend variation of a specific tag in different time periods is also analyzed. The evaluation shows the recommendation accuracy of the proposed approach is about 75%. Besides, the case discussion also proves the proposed approach can track the social trends. (C) 2011 Elsevier Ltd. All rights reserved.
Two distinct ballistic processes in graphene at the Dirac point
(2011-09-15)
Lewkowicz, M.
;
Rosenstein, B.
;
Nghiem, D.
;
電子物理學系
;
Department of Electrophysics
The dynamical approach is applied to ballistic transport in mesoscopic graphene samples of length L and contact potential U. At times shorter than both relevant time scales, the flight time t(L) = L/v(g) (v(g) is Fermi velocity) and t(U) = (h) over bar /U, the major effect of the electric field is to create electron-hole pairs, i.e., causing interband transitions. In linear response, this leads (for width W >> L) to conductivity sigma(2) = pi/2 e(2)/h. On the other hand, at times lager than the two scales, the mechanism and value are different. It is shown that the conductivity approaches its intraband value, equal to the one obtained within the Landauer-Butticker approach resulting from evanescent waves. It is equal to sigma(1) = 4/pi e(2)/h for W >> L and t(U) << t(L). The interband transitions, within linear response, are unimportant in this limit. Between these extremes there is a crossover behavior dependent on the ratio between the two time scales t(L)/t(U). At strong electric fields (beyond linear response) the interband process dominates. The electron-hole mechanism is universal, namely, does not depend on geometry (aspect ratio, topology of boundary conditions, properties of leads), while the evanescent modes mechanism depends on all of them. On basis of the results we determine that while in absorption measurements and in dc transport in suspended graphene sigma(2) was measured, sigma(1) would appear in experiments on small ballistic graphene flakes on substrate.
Creating the aspired intelligent assessment systems for teaching materials
(2011-09-15)
Chen, Cheng-Hsiung
;
Tzeng, Gwo-Hshiung
;
科技管理研究所
;
Institute of Management of Technology
The core objective of the Nine-Year Integrated Curriculum for primary schools is to "enable students to demonstrate their talents instead of just scoring high on exams" around the world. The determining factor in education reform is to declare the competence indicators of necessary educational behavior in primary and junior high school. In the reform process, for all domains, the enriched rate of competence indicators for educational materials and methods is very meaningful. Because educational materials and methods in different domains have their own style, we should evaluate these teaching materials separately. Thus, in this research we propose a novel MCDM (Multiple Criteria Decision Making) framework for evaluating, comparing, and improving the effectiveness of competence indicators in the various publications for teaching materials in primary school based on different viewpoints. The ANP (Analysis Network Process) weights are based on the DEMATEL technique with the MCDM method for resolving the problems of dependence and feedback among criteria. Then, a VIKOR technique with ANP weights is proposed for addressing and reducing the performance gaps for each criterion, thus hopefully improving, re-configuring and selecting the aspired Intelligent Assessment Systems (IAS) for teaching materials. An empirical study of Mandarin Chinese based on this system design of three publishers is illustrated to verify the effectiveness of the proposed method. The results can improve the efficiency and quality of the authored Mandarin Chinese teaching materials and may extend to other Learning Areas. (C) 2011 Elsevier Ltd. All rights reserved.
Curcumin enhances the mitomycin C-induced cytotoxicity via downregulation of MKK1/2-ERK1/2-mediated Rad51 expression in non-small cell lung cancer cells
(2011-09-15)
Ko, Jen-Chung
;
Tsai, Min-Shao
;
Weng, Shao-Hsing
;
Kuo, Ya-Hsun
;
Chiu, Yu-Fan
Curcumin (diferuloylmethane), a major active component of turmeric (Curcuma longa), has been reported to suppress the proliferation of a wide variety of tumor cells. Rad51 is a key protein in the homologous recombination (HR) pathway of DNA double-strand break repair, and HR represents a novel target for cancer therapy. A high expression of Rad51 has been reported in chemo- or radio-resistant carcinomas. Therefore, in the current study, we will examine whether curcumin could enhance the effects of mitomycin C (MMC), a DNA interstrand cross-linking agent, to induce cytotoxicity by decreasing Rad51 expression. Exposure of two human non-small lung cancer (NSCLC) cell lines (A549 and H1975) to curcumin could suppress MMC-induced MKK1/2-ERK1/2 signal activation and Rad51 protein expression. Enhancement of ERK1/2 activation by constitutively active MKK1/2 (MKK1/2-CA) increased Rad51 protein levels in curcumin and MMC co-treated human lung cells. Moreover, the synergistic cytotoxic effect induced by curcumin combined with MMC was decreased by MKK1-CA-mediated enhancement of ERK1/2 activation by a significant degree. In contrast, MKK1/2 inhibitor, U0126 was shown to augment the cytotoxicity of curcumin and MMC through downregulation of ERK1/2 activation and Rad51 expression. Depletion of endogenous Rad51 expression by siRad51 RNA transfection significantly enhanced MMC and/or curcumin induced cell death and cell growth inhibition. In contrast, an overexpression of Rad51 protected lung cancer cells from synergistic cytotoxic effects induced by curcumin and MMC. We concluded that Rad51 inhibition may be an additional action mechanism for enhancing the chemosensitization of MMC by curcumin in NSCLC. (C) 2011 Elsevier Inc. All rights reserved.