Browsing by Author "Chang, CA"

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A synthetic complement C1q-like peptide selectively interacts with immune complexes
(1998-12-01)
Chan, EC
;
Pan, MZ
;
Chang, CA
;
Wu, TZ
;
Kuo, YB
A water-soluble peptide possessing an immune complex selective affinity was synthesized and its primary structure established as: Leu-Glu-Gln-Gly-Glu-Asn-Val-Phe-Leu-Gln-Ala-Thr-Ser-Asp-Asp-Cys. This peptide, designated as C1q-like peptide (CLP), represents a possible immune complex binding epitope of complement C1q. CLP has a hydrophilicity value of 0.21. At 0.5 mu M, it inhibited by 50% natural human C1q from binding to horseradish peroxidase-rabbit anti-peroxidase immune complex. CLP failed to inhibit Staphylococcus aureus protein A from binding monomeric IgG. When coated to a microplate, CLP showed selective binding to the immune complex, and could be used for application in immunochemical detection of immune complex.
Acid-catalysed dissociation of the copper(II) and lead(II) complexes of macrocyclic diazapolyoxa-N,N'-diacetic acids
(1997-04-07)
Laing, JL
;
Taylor, RW
;
Chang, CA
;
生物科技學系
;
Department of Biological Science and Technology
The dissociation rate constants of the complexes of Cu2+ and Pb2+ with 1,4,10,13-tetraoxa-7,16-diazacyclo-octadecane-N,N'-diacetic acid (H2L2) and the copper(II) complex of 1,4,10-trioxa-7,13-diazacyclopentadecane-N,N'-diacetic acid (H2L1) have been determined at 25.0 degrees C in aqueous media (I = 0.20 mol dm(-3), LiClO4). In the presence of an excess of strong acid, 1.3-100 mmol dm(-3) HClO4, the dissociation reactions follow the rate law -d[ML](T)/dt = (k(d) + K(MHL)k(H1)[H+] + K(MHL)k(H2)[H+](2))/(1 + K-ML[H+])[ML](T) where [ML](T) = [ML] + [MHL], k(H1), and k(H2) are the respective rate constants for the specified reactions and MHL is the protonated metal-ligand complex. The values of k(Hi) (i = 1 or 2) decrease according to the sequence [PbL2] much greater than [CuL2] > [CuL1]. The formation rate constants for M2+ reacting with (HL2)(-) and H2L2 are (2.3-4.2) x 10(8) and (2.2-17) x 10(2) dm(3) mol(-1), respectively. The relatively low values for the diprotonated species are attributed to an unfavourable equilibrium concentration of the reactive species -O2CCH2N(CH2CH2OCH2CH2OCH2CH2)(2)N+HCH2CO2H. The dissociation of [PbL2], but neither of the copper complexes, is subject to general acid catalysis (HA = MeCO2H and ClCH2CO2H). The exchange reaction of [PbL2] with Cu2+ in buffered (MeCO2H-MeCO2-) mildly acidic media shows a first-order dependence on [H+], [MeCO2H] and [Cu2+].
Acid-catalysed dissociation of the copper(II) and lead(II) complexes of macrocyclic diazapolyoxa-N,N'-diacetic acids
(1997-04-07)
Laing, JL
;
Taylor, RW
;
Chang, CA
;
生物科技學系
;
Department of Biological Science and Technology
The dissociation rate constants of the complexes of Cu2+ and Pb2+ with 1,4,10,13-tetraoxa-7,16-diazacyclo-octadecane-N,N'-diacetic acid (H2L2) and the copper(II) complex of 1,4,10-trioxa-7,13-diazacyclopentadecane-N,N'-diacetic acid (H2L1) have been determined at 25.0 degrees C in aqueous media (I = 0.20 mol dm(-3), LiClO4). In the presence of an excess of strong acid, 1.3-100 mmol dm(-3) HClO4, the dissociation reactions follow the rate law -d[ML](T)/dt = (k(d) + K(MHL)k(H1)[H+] + K(MHL)k(H2)[H+](2))/(1 + K-ML[H+])[ML](T) where [ML](T) = [ML] + [MHL], k(H1), and k(H2) are the respective rate constants for the specified reactions and MHL is the protonated metal-ligand complex. The values of k(Hi) (i = 1 or 2) decrease according to the sequence [PbL2] much greater than [CuL2] > [CuL1]. The formation rate constants for M2+ reacting with (HL2)(-) and H2L2 are (2.3-4.2) x 10(8) and (2.2-17) x 10(2) dm(3) mol(-1), respectively. The relatively low values for the diprotonated species are attributed to an unfavourable equilibrium concentration of the reactive species -O2CCH2N(CH2CH2OCH2CH2OCH2CH2)(2)N+HCH2CO2H. The dissociation of [PbL2], but neither of the copper complexes, is subject to general acid catalysis (HA = MeCO2H and ClCH2CO2H). The exchange reaction of [PbL2] with Cu2+ in buffered (MeCO2H-MeCO2-) mildly acidic media shows a first-order dependence on [H+], [MeCO2H] and [Cu2+].
An aberrant autocrine activation of the platelet-derived growth factor alpha-receptor in follicular and papillary thyroid carcinoma cell lines
(2006-01-18)
Chen, KT
;
Lin, JD
;
Liou, MJ
;
Weng, HF
;
Chang, CA
Platelet-derived growth factor receptor (PDGFR) can bind to its ligand and consequently possess a kinase activity, and which is associated with the carcinogenesis of different cell types, including astrocytomas, oligodendrogliomas. and glioblastoma. In a cDNA microarray analysis, we observe the over-expressed mRNA of both PDGF-A and PDGF-alpha receptor in thyroid carcinoma cells. And the elevated protein expressions of PDGF-A and PDGF-alpha receptor in thyroid carcinoma cells were also confirmed by a Western blot analysis. The phosphorylation of PDGF-alpha receptor evaluated by an antibody against Tyr 720-phosphate was found in thyroid carcinoma cells. The tyrosine kinase activity of PDGF-alpha receptor was inhibited by tyrphostin AG1295 and showed a dose-dependent inhibition for the proliferation of thyroid carcinoma cells. These findings imply that autocrine activation of PDGF-alpha receptor plays a crucial role in the carcinogenesis of thyroid cells. (c) 2005 Elsevier Ireland Ltd. All rights reserved.
Capillary electrophoresis, potentiometric and laser excited luminescence studies of lanthanide(III) complexes of 1,7-dicarboxymethyl-1,4,7,10-tetraazacyclododecane (DO2A)
(1998-10-07)
Chang, CA
;
Chen, YH
;
Chen, HY
;
Shieh, FK
;
生物科技學系
The protonation constants of the ligand 1,7-dicarboxymethyl-1,4,7,10-tetraazacyclododecane (DO2A) were redetermined by the potentiometric pH titration method (log K 10.94, 9.55, 3.85, 2.55) and the macrocycle ring protonation sites have also been confirmed by NMR techniques to be the secondary amine nitrogen atoms. The stability constants of calcium(II) and all trivalent lanthanide (Ln(3+)) metal complexes of DO2A (Ca2+, log K-ML 7.16; Ln(3+), log K-ML 10.94-13.31) were determined by the potentiometric pH titration and capillary electrophoresis methods, respectively. In general, the stabilities of the Ln(DO2A)(+) complexes increase with increasing atomic number for the lighter lanthanides (La3+-Sm3+) and remain relatively unchanged for the heavier lanthanides (Eu3+-Lu3+). Laser-excited spectroscopy of the F-7(o) --> D-5(o) transition of Eu3+ is used to study the aqueous Eu3+-DO2A complex system. At low pH (e.g. pH 5-6) Eu3+ forms a 1:1 species with the ligand DO2A, presumably Eu(DO2A)(H2O)(q)(+), where q is the number of inner-sphere coordinated water molecules. As the solution pH increases the hydrolysis product, Eu(DO2A)(OH)(H2O)(q-1), is formed. Lifetime measurements of each species in H2O and D2O allow the determination of the corresponding number of inner-sphere coordinated water molecules to be 3.0 and 2.6, consistent with the proposed structures (i.e. q = 3). The first hydrolysis constant (pK(h)) is estimated to be 8.1 +/- 0.3.
Dissociation kinetics of cerium(III) complexes of macrocyclic polyaza polycarboxylate ligands TETA and DOTA
(2000-08-01)
Chang, CA
;
Liu, YL
;
生物科技學系
;
Department of Biological Science and Technology
The acid-catalyzed dissociation rate constants of the cerium(III) complexes of 1,4,8,11-tetraazacyclotetradecane-1,4, 8,11-tetraacetic acid (TETA) and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) have been determined at four different temperatures (i.e., 25.0 degreesC, 32.0 degreesC, 39.0 degreesC, 45.0 degreesC) in aqueous media (mu = 0.10 M, HCl/KCl) to obtain additional kinetic data and to evaluate possible effects of ligand pre-organization for metal ion complexation. The rates are much faster for Ce(TETA)(-) than for Ce(DOTA)(-), indicating the lower thermodynamic stability of the former. In the presence of excess strong acid, 0.1 - 1.0 M HCl, the dissociation reactions follow the rate law: -d[ML]T/dt = (k(d) + k(H)[H+])[ML](T) and -d[ML]T/dt = (k(H)[H+] + k(H2)[H+](2))[ML](T), respectively, where k(d) is acid-independent dissociation reaction rate constant and k(H) and k(H2) are the respective dissociation rate constants for the pathways involving monoprotonated and diprotonated species. The rate activation parameters, DeltaH(not equal), DeltaS(not equal) and DeltaG(not equal), for each dissociation pathway have been obtained and their values are consistent with the proposed mechanisms. In particular, the rate difference between Ce(TETA)(-) and Ce(DOTA)(-) for the monoprotonated complex dissociation pathway is mainly due to difference in DeltaH(H)(not equal). If has been concluded that ligand pre-organization results in more stable complexes and slower complex dissociation rates.
Dissociation kinetics of nickel(II), zinc(II) and cadmium(II) complexes of 1,7-diaza-4,10,13-trioxacyclopentadecane-N,N'-diacetic acid and 1,10-diaza-4,7,13,16-tetraoxacyclooctadecane-N,N'-diacetic acid
(1996-10-01)
Chang, CA
;
交大名義發表
;
生物科技學系
;
National Chiao Tung University
;
Department of Biological Science and Technology
The dissociation kinetics of the complexes of nickel(II), zinc(II) and cadmium(II) of 1,7-diaza-4,10,13-trioxacyclopentadecane-N,N'-diacetic acid (K21DA) and 1,10-diaza-4,7,13,16-tetraoxacyclooctadecane-N,N'-diacetic Acid (K22DA) were studied in constant ionic strength aqueous medium with various [H+]-range, i.e., (0.88-53.9) x 10(-5) M and (0.5-7.5) x 10(-3) M. Copper(II) was used as the scavenger of free ligand and the rates of dissociation of these complexes have been found to be independent of [Cu2+]. All the complexes exhibit acid-independent and acid-dependent pathways. For NiK21DA, CdK21DA and CdK22DA complexes, the acid-dependent rates are linear functions of [H+]. For NiK22DA and ZnK21DA complexes, a saturation kinetics is observed, i.e., [H+]-dependence at low [H+] and [H+]-independent at high [H+]. The rationalization of such different observations is proposed to be due to difference in complex solution structures rather than the thermodynamic stabilities. Influence of acetate content in the buffer, temperature, and total electrolyte concentration on the late of dissociation has also been investigated and discussed.
Down-regulation of matrix Gla protein messenger RNA in human colorectal adenocarcinomas
(2001-04-10)
Fan, CW
;
Sheu, DL
;
Fan, HA
;
Hsu, KC
;
Chang, CA
Matrix Gla protein (MGP) is a vitamin K-dependent extracellular matrix protein commonly found in a variety of tissues. In this study, we describe the potential use of MGP gene expression as the tumor marker of colorectal cancer. A decrease in expression of the MGP gene was also discovered in colorectal cancer using differential screening of cDNA libraries. The MGP expression in 80 human colorectal adenocarcinomas was quantified by a Northern blot analysis to better define the expression pattern of MGP in colorectal cancer. The expression of MGP mRNA was reduced in 63 of 80 (79%) colorectal adenocarcinomas (P < 0.001) as compared to the mRNA in adjacent normal tissue, implying that a decrease in MGP expression is associated with colorectal cancer development. The proportion of tumors with downregulated expression of MGP was lower in Duke's A/B than Duke's C/D (34 of 47 versus 26 of 33, respectively) tumors and was lower in moderate differentiation than poor differentiation (44 of 64 versus 16 of 16, respectively). However, chi (2) analysis does not reveal any correlation between a loss of MGP expression and tumor progression or differentiation state. In conclusion, the downregulation of MGP mRNA generally occurs in colorectal adenocarcinomas. Although the role of MGP in cancer development is unknown, the reduced expression of MGP may be used to distinguish the normal colorectal cells from malignant cells. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.
Effects of ligand chain length and terminal N-alkylation on the protonation constants and stability constants of some transition metal complexes of linear tetraaza and pentaaza ligands
(1998-12-01)
Chang, CA
;
Shieh, FK
;
Liu, YL
;
Chung, CS
;
生物科技學系
A number of terminal N-alkylated linear tetraaza and pentaaza ligands were prepared. Their ligand protonation constants and some transition and post-transition metal (Ni2+, Cu2+, Zn2+, and Cd2+) complex stability constants were determined by potentiometric titration methods. In general, methylation and ethylation at the terminal nitrogen atoms caused the corresponding ligand nitrogen basicity to increase; however, the corresponding metal complex stabilities were decreased compared to the non-alkylated structural analogs, presumably due to a steric effect.
Effects of ligand chain length and terminal N-alkylation on the protonation constants and stability constants of some transition metal complexes of linear tetraaza and pentaaza ligands
(1998-12-01)
Chang, CA
;
Shieh, FK
;
Liu, YL
;
Chung, CS
;
生物科技學系
A number of terminal N-alkylated linear tetraaza and pentaaza ligands were prepared. Their ligand protonation constants and some transition and post-transition metal (Ni2+, Cu2+, Zn2+, and Cd2+) complex stability constants were determined by potentiometric titration methods. In general, methylation and ethylation at the terminal nitrogen atoms caused the corresponding ligand nitrogen basicity to increase; however, the corresponding metal complex stabilities were decreased compared to the non-alkylated structural analogs, presumably due to a steric effect.
Effects of recombinant lysostaphin on cytotoxicity and interleukin-8 level in normal human epidermal keratinocytes cell line
(1998-11-01)
Chan, EC
;
Chang, CA
;
Wu, TZ
;
Lin, YL
;
生物科技學系
The normal human epidermal keratinocyte (NHEK) was used to evaluate the cytotoxicity of recombinant lysostaphin. As determined with the Neutral Red (NR) cytotoxicity assay, the midpoint toxicity value (NR50) after 48 h exposure was 16 +/- 0.4 g lysostaphin/l. Lysostaphin cytotoxicity effect is much less than the surface active agent, sodium laurate. However, the NR,, value after 48-h exposure was 1.9 +/- 0.02 g/l for S. aureus lysate derived from the bacterial lytic action of lysostaphin. A linear increase in interleukin-8 (IL-8) level in NHEK cells from resting levels of 65 +/- 3 pg/ml to peak of 760 +/- 15 pg/ml during the first 9 hours was noted for the cells treated with 800 mg lysostaphin/l. S. aureus lysate has the same effect on the induction of IL-8 levels. The induced rises in IL-8 were lysostaphin and S. aureus lysate concentration dependence.
Effects of recombinant lysostaphin on cytotoxicity and interleukin-8 level in normal human epidermal keratinocytes cell line
(1998-11-01)
Chan, EC
;
Chang, CA
;
Wu, TZ
;
Lin, YL
;
生物科技學系
The normal human epidermal keratinocyte (NHEK) was used to evaluate the cytotoxicity of recombinant lysostaphin. As determined with the Neutral Red (NR) cytotoxicity assay, the midpoint toxicity value (NR50) after 48 h exposure was 16 +/- 0.4 g lysostaphin/l. Lysostaphin cytotoxicity effect is much less than the surface active agent, sodium laurate. However, the NR,, value after 48-h exposure was 1.9 +/- 0.02 g/l for S. aureus lysate derived from the bacterial lytic action of lysostaphin. A linear increase in interleukin-8 (IL-8) level in NHEK cells from resting levels of 65 +/- 3 pg/ml to peak of 760 +/- 15 pg/ml during the first 9 hours was noted for the cells treated with 800 mg lysostaphin/l. S. aureus lysate has the same effect on the induction of IL-8 levels. The induced rises in IL-8 were lysostaphin and S. aureus lysate concentration dependence.
Electrochemical study on screen-printed carbon electrodes with modification by iron nanoparticles in Fe(CN)(6)(4-/3-) redox system
(2005-10-01)
Lee, SH
;
Fang, HY
;
Chen, WC
;
Lin, HM
;
Chang, CA
The remarkable enhancement of electron transfer on screen-printed carbon electrodes (SPCEs) with modification by iron nanoparticles (Fe-nano), coupled with Fe(CN)(6)(4-/3-) redox species, was characterized with an increase of electroactive area (A(ea)) at electrode surface together with a decrease of heterogeneous. electron transfer rate constant (k degrees) in the system. Hence, Fe-nano-Fe(CN)(6)(3-) SPCEs with deposition of glucose oxidase (GOD) demonstrated a higher sensitivity to various glucose concentrations than Fe(CN)(6)(3-)/GOD-deposited SPCEs. In addition, an inhibited diffusion current from cyclic voltammograms was also observed with an increase in redox concentration and complicated the estimation of A(ea). Further analysis by the electrochemical impedance method, it was shown that this effect might be resulted from the electrode surface blocking by the products of activated complex decomposition.
Expression and purification of human placenta lactogen in Escherichia coli
(2006-04-01)
Lan, PC
;
Tseng, CF
;
Lin, MC
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Chang, CA
;
生物科技學系
There are many growth factors secreted by placenta including growth hormone, placenta lactogen (PL), prolactin, follicle stimulating hormone, luteinizing hormone, thyroid stimulating hormone, and chorionic gonadotropin. For a systematic study of how these growth factors work together to result in the various biological functions and future clinical applications, it is needed to produce enough quantities of each protein. In this paper, we report the cloning of human PL (hPL) and expression by Escherichia coli (E coli). Four kinds of expression vectors containing the hPL gene were transformed into several kinds of suitable host strains and grown at 37 and/or 30 degrees C. Determination of the yield of recombinant hPL by SDS-PAGE reveals that among the various conditions, pQE30-PL in E. coli strain M15[pREP4] expressed the largest amount of recombinant hPL at 37 degrees C. However, the expressed recombinant hPL was accumulated in inclusion body forms. The inclusion bodies were solubilized in 8 M urea and purified by a His(6) tagged affinity column under denaturing condition and the final yield of hPL was determined to be 48 mg/L. Intra-chain disulfide bonds could be formed either by oxidation in the refolding buffer or by air oxidation in the presence of urea. The biological activity was examined by the fact that hPL could stimulate erythroid maturation by the formation of hemoglobin in K-562 cells in the presence of erythropoietin. Initial optimization studies resulted in the production of 282.4 mg/L of hPL. (c) 2005 Elsevier Inc. All rights reserved.
Helicobacter pylori induces gene expression in human gastric cells identified by mRNA differential display
(1996-11-12)
Wong, L
;
Lue, MY
;
Chang, CA
;
Lin, YL
;
Chan, EC
Changes in gene expression patterns in gastric cells infected with Helicobacter pylori were characterized by means of mRNA differential display. Total RNA preparations were extracted from the H. pylori infected gastric cells and paired non-infected cells, and were probed with candidate clones identified after screening up to 6,000 mRNA species. Among them, four clones, 04G-1, 04G-2, 01G-1, and Cppa-2 show significant expression in the infected cells by Northern blot analysis, and they are 199 bp, 196 bp, 228 bp, and 276 bp in length, respectively. Database search revealed that nucleotide sequences of these clones share very low identity with any known sequence. These results indicate that H. pylori can significantly affect gene expression in gastric cells. Furthermore mRNA differential display can be used in pathogenesis studies to identify new genes in gastric cells in response to insults such as H. pylori. (C) 1996 Academic Press, Inc.
Helicobacter pylori induces gene expression in human gastric cells identified by mRNA differential display
(1996-11-12)
Wong, L
;
Lue, MY
;
Chang, CA
;
Lin, YL
;
Chan, EC
Changes in gene expression patterns in gastric cells infected with Helicobacter pylori were characterized by means of mRNA differential display. Total RNA preparations were extracted from the H. pylori infected gastric cells and paired non-infected cells, and were probed with candidate clones identified after screening up to 6,000 mRNA species. Among them, four clones, 04G-1, 04G-2, 01G-1, and Cppa-2 show significant expression in the infected cells by Northern blot analysis, and they are 199 bp, 196 bp, 228 bp, and 276 bp in length, respectively. Database search revealed that nucleotide sequences of these clones share very low identity with any known sequence. These results indicate that H. pylori can significantly affect gene expression in gastric cells. Furthermore mRNA differential display can be used in pathogenesis studies to identify new genes in gastric cells in response to insults such as H. pylori. (C) 1996 Academic Press, Inc.
Identifying differentially expressed genes associated with metastasis of follicular thyroid cancer by cDNA expression array
(2001-01-01)
Chen, KT
;
Lin, JD
;
Chao, TC
;
Hsueh, C
;
Chang, CA
Patients with follicular thyroid carcinoma have a higher incidence of metastasis than papillary thyroid carcinoma when thyroid cancer is diagnosed. The cDNA expression array technology is utilized herein to profile differentially expressed genes from metastatic human follicular thyroid carcinoma and reveal new tumor markers as well as target genes for therapeutic intervention. Tissue samples were obtained during surgical resection of the thyroid follicular carcinoma and metastatic tissue in the brain of the same patient. Two identical Atlas human cDNA expression arrays were hybridized with P-32-labeled cDNA probes derived from RNA of either primary thyroid cancer or metastatic tissue. Parallel analysis of the hybridized signals allowed us to identify the alteration of gene expression in the metastasis process. Eighteen genes significantly overexpressed and 40 genes significantly underexpressed were identified in the metastatic thyroid cancer. Genes that displayed an altered expression were associated with the processes of cell cycle regulation, apoptosis, DNA damage response, angiogenesis, cell adhesion and mobility, invasion, and immune response. An expression profile of genes that are associated with metastasis process of follicular thyroid cancer was also discussed. Further investigation is required to understand the precise relationship between the altered expression of these genes and the metastasis process of follicular thyroid cancer.
Induction of apoptosis in MCF-7 human breast cancer cells by phytochemicals from Anoectochilus formosanus
(2004-01-01)
Shyur, LF
;
Chen, CH
;
Lo, CP
;
Wang, SY
;
Kang, PL
The antitumor activity of Anoectochilus formosanus Hayata (Orchidaceae), a popularly used folk medicine in the treatment of cancers in Asia, was investigated in MCF-7 human mammary carcinoma cells. Plant extracts of A. formosanus were observed to induce apoptosis of MCF-7 cells as evidenced by cell-morphological changes, an early redistribution of plasma membrane phosphatidylserine, and DNA content distribution studies. Bioactivity-guided fractionation of A. formosanus extracts produced a specific ethyl acetate (EA)-partitioned fraction in which apoptotic activity was enriched. The chemical profile and candidate index compounds of the active EA fraction were obtained using HPLC and various spectral analyses. Western blot analysis showed that upon treatment of MCF-7 cells with the EA fraction, cleavage of pro-caspases-8, -9, and -7, and poly(ADP-ribose) polymerase as well as significant release of mitochondrial cytochrome c into the cytosol were readily observed. Flow cytometry showed that the Fas ligand protein was overexpressed in EA-treated MCF-7 cells. Functional genomic studies indicated that specific genes related to cytoskeleton rearrangement, apoptotic signal transduction, and various transcription factors were differentially regulated in EA-treated MCF-7 cells. Putative apoptotic signaling pathways of MCF-7 cells in response to the EA extract of A. formosanus are proposed. Copyright (C) 2004 National Science Council, ROC and S. Karger AG, Basel.
Laser-excited luminescence study of aqueous solution properties of the Eu3+-D02A system
(1997-04-13)
Chang, CA
;
Chen, YH
;
生物科技學系
;
Department of Biological Science and Technology
Ligand preorganization in metal ion complexation: Molecular mechanics/dynamics, kinetics, and laser-excited luminescence studies of trivalent lanthanide complex formation with macrocyclic ligands TETA and DOTA
(2001-07-02)
Chang, CA
;
Liu, YL
;
Chen, CY
;
Chou, XM
;
生物科技學系
The molecular mechanics and dynamics calculations, kinetics, and laser-excited luminescence studies were carried out for trivalent lanthanide (Ln(3+)) complexes of macrocyclic polyaminopolycarboxylate ligands TETA and DOTA (where TETA is 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetraacetic acid and DOTA is 1,4,7,10-tetraazacy-clododecane-1,4,7,10-tetraacetic acid) to further understand the observed thermodynamic, kinetic, and structural properties and to examine how ligand preorganization affects metal ion complexation. Excitation spectroscopy (emission monitored at 614.0 nm) of the F-7(0) - D-5(0)- transition of Eu3+ was used to study the aqueous properties of the Eu3+-TETA system. A stopped-flow spectrophotometric method was used to study the formation kinetics of the aqueous Ce3+-TETA/DOTA systems in the pH range 6.1-6.7. Molecular mechanics calculation results are consistent with the proposed mechanism of Ln(DOTA)- formation, i.e., formation of a. carboxylate O-bonded precursor, followed by metal ion moving into the preformed macrocyclic cavity. For Ln(TETA)- formation, at least two carboxylate O-bonded intermediates have been predicted and Ln(3+) ion assisted reorganization of the TETA ligand is present. The calculated bond distances and overall structures of Ln(DOTA)- and Ln(TETA)were in agreement with the single-crystal and solution NMR structural data. The origin of thr difference in thermodynamic stability of Ln(DOTA)- and Ln(TETA)- complexes and the corresponding formation intermediates is mainly due to the differences in water-occupancy energy (i.e., whether there is an apical coordinated water molecule), the ligand strain energy, and the cation-ligand interaction energy. Kinetic studies revealed that the formation rates of the Ce(TETA)- complex are smaller at lower pH and temperature but become greater at higher pH and temperature, as compared to those of the Ce(DOTA)- complex. This is attributed to the lanthanide ion and both mono- and di-hydroxide ion assisted TETA conformational reorganization and higher kinetic activation parameters. The presence of a di-hydroxide ion assisted intermediate rearrangement pathway could make the Ce(TETA)- complex formation rate faster at higher pH, and the higher activation barrier makes Cr(TETA)complex formation rate slower at lower pH, as compared to those of the Ce(DOTA)- complex.