Functional roles of ALMT-type anion channels in malate-induced stomatal closure in tomato and Arabidopsis.

Guard-cell-type aluminium-activated malate transporters (ALMTs) are involved in stomatal closure by exporting anions from guard cells. However, their physiological and electrophysiological functions are yet to be explored. Here, we analysed the physiological and electrophysiological properties of the ALMT channels in Arabidopsis and tomato (Solanum lycopersicum). SlALMT11 was specifically expressed in tomato guard cells. External malate-induced stomatal closure was impaired in ALMT-suppressed lines of tomato and Arabidopsis, although abscisic acid did not influence the stomatal response in SlALMT11-knock-down tomato lines. Electrophysiological analyses in Xenopus oocytes showed that SlALMT11 and AtALMT12/QUAC1 exhibited characteristic bell-shaped current-voltage patterns dependent on extracellular malate, fumarate, and citrate. Both ALMTs could transport malate, fumarate, and succinate, but not citrate, suggesting that the guard-cell-type ALMTs are dicarboxylic anion channels activated by extracellular organic acids. The truncation of acidic amino acids, Asp or Glu, from the C-terminal end of SlALMT11 or AtALMT12/QUAC1 led to the disappearance of the bell-shaped current-voltage patterns. Our findings establish that malate-activated stomatal closure is mediated by guard-cell-type ALMT channels that require an acidic amino acid in the C-terminus as a candidate voltage sensor in both tomato and Arabidopsis.

Structural Approach to Understanding the Formation of Amorphous Metal Hydroxides.

This study investigates the formation of amorphous tetravalent metal hydroxides, M(OH)4, based on the structural analysis by small- and wide-angle X-ray scattering (SWAXS) and on the electrical potential charge near the surface of M(OH)4 particles. The amorphous zirconium hydroxide solid phases that aged in NaCl and CaCl2 solutions at 25 °C exhibited a hierarchical structure consisting of primary particles of a few nanometers in size and their aggregates more than 100 nm in size. The SWAXS profiles suggested that the size of the primary particles depends on the ionic strength and electrolytes in the sample solutions. The smaller size of the primary particles observed in solutions with higher ionic strength can be explained by the thinner electrical double layer. Additionally, we focused on the ζ potentials of M(OH)4 suspensions in NaCl, NaNO3, and CaCl2 solutions. With the aid of reference systems of metal oxides, MO2, it was found that the ζ potentials were well interpreted by a traditional surface ionization and complexation model, and the size distributions of large aggregates were explained by the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory with the ζ potential values. The present study suggests the formation mechanism of amorphous metal hydroxides through a combination of structural analysis and investigation of electrical potentials.

Physiological Role of Aerobic Fermentation Constitutively Expressed in an Aluminum-Tolerant Cell Line of Tobacco (Nicotiana tabacum).

Aluminum (Al)-tolerant tobacco cell line ALT301 derived from SL (wild-type) hardly exhibits Al-triggered reactive oxygen species (ROS) compared with SL. Molecular mechanism leading to this phenotype was investigated comparatively with SL. Under normal growth condition, metabolome data suggested the activation of glycolysis and lactate fermentation but the repression of the tricarboxylic acid (TCA) cycle in ALT301, namely aerobic fermentation, which seemed to be transcriptionally controlled partly by higher expression of genes encoding lactate dehydrogenase and pyruvate dehydrogenase kinase. Microarray and gene ontology analyses revealed the upregulation of the gene encoding related to APETALA2.3 (RAP2.3)-like protein, one of the group VII ethylene response factors (ERFVIIs), in ALT301. ERFVII transcription factors are known to be key regulators for hypoxia response that promotes substrate-level ATP production by glycolysis and fermentation. ERFVIIs are degraded under normoxia by the N-end rule pathway of proteolysis depending on both oxygen and nitric oxide (NO), and NO is produced mainly by nitrate reductase (NR) in plants. In ALT301, levels of the NR gene expression (NIA2), NR activity and NO production were all lower compared with SL. Consistently, the known effects of NO on respiratory pathways were also repressed in ALT301. Under Al-treatment condition, NO level increased in both lines but was lower in ALT301. These results suggest that the upregulation of the RAP2.3-like gene and the downregulation of the NIA2 gene and resultant NO depletion in ALT301 coordinately enhance aerobic fermentation, which seems to be related to a higher capacity to prevent ROS production in mitochondria under Al stress.

AtALMT3 is Involved in Malate Efflux Induced by Phosphorus Deficiency in Arabidopsis thaliana Root Hairs.

Under phosphorus (P)-deficient conditions, organic acid secretion from roots plays an important role in P mobilization from insoluble P in the soil. In this study, we characterized AtALMT3, a homolog of the Arabidopsis thaliana aluminum-activated malate transporter family gene. Among the 14 AtALMT family genes, only AtALMT3 was significantly up-regulated in P-deficient roots. AtALMT3 promoter::ß-glucuronidase is expressed in the epidermis in roots, especially in root hair cells. AtALMT3 protein was localized in the plasma membrane and in small vesicles. Fluorescence of AtALMT3::GFP was not observed on the vacuole membrane of protoplast after lysis, indicating that AtALMT3 localizes mainly in the plasma membrane. Compared with the wild-type (WT) line, malate exudation in the AtALMT3-knockdown line (atalmt3-1) and overexpression line (atalmt3-2) under P deficiency were, respectively, 37% and 126%. In contrast, no significant difference was found in citrate exudation among these lines. The complementation of the atalmt3-1 line with AtALMT3 recovered the malate exudation to the level of the WT. Taken together, these results suggest that AtALMT3 localized in root hair membranes is involved in malate efflux in response to P deficiency.

Structural Approach to Understanding the Solubility of Metal Hydroxides.

We report the hierarchical structure of zirconium hydroxide after aging at different temperatures to elucidate the factors governing zirconium solubility in aqueous solutions. Zirconium hydroxide solid phases after aging at 25, 40, 60, and 90 °C under acidic to alkaline conditions were investigated using extended X-ray absorption fine structure (EXAFS), wide- and small-angle X-ray scattering (WAXS and SAXS), and transmission electron microscopy (TEM) techniques to reveal the bulk and surface structures of the solid phases from the nanoscale to sub-microscale. After aging at 25 °C, the fundamental building unit of the solid phase was considered to be tetrameric and dimeric hydroxide species. These polynuclear species formed amorphous primary particles that are approximately 3 nm in size, which in turn formed aggregates that are hundreds of nanometers in size. This hierarchical structure was found to be stable up to 60 °C under acidic and neutral conditions and up to 40 °C under alkaline conditions. After aging at 90 °C under acidic conditions and at 60 and 90 °C under alkaline conditions, the WAXS and EXAFS measurements suggested the crystallization of the solid phase. The SAXS profiles and TEM observations supported the existence of crystallized large particles about 60 nm in size, and the appearance of the Guinier region in the SAXS profiles indicated that the crystallization of the amorphous primary particles leads to the reduction of the size of the large aggregates. The transformation of the solid-phase structure by temperature was discussed in relation to the solubility product to understand the solubility-limiting solid phase. The solubility of zirconium hydroxide after aging at different temperatures was governed not only by the size of the amorphous primary particles or crystallized large particles but also by their surface configuration.

The EQ-5D-5L in patients admitted to a hospital in Japan with recent spinal cord injury: a descriptive study.

STUDY DESIGN: Descriptive study. OBJECTIVE: To demonstrate Euro Quality of Life 5-dimensional 5-level (EQ-5D-5L) by severity level at the acute stage and discharge in patients with traumatic spinal cord injury (SCI). SETTING: Spinal Injuries Center, Fukuoka, Japan. METHODS: Patients with traumatic SCI who completed the EQ-5D-5L instrument at the acute stage and discharge were divided into four groups according to severity (severity group G1; C1-C4 ASIA Impairment Scale (AIS) A, B, and C, G2; C5-C8 AIS A, B, and C, G3; T1-S5 AIS A, B, and C, G4; all AIS D). All data were extracted from the Japan single-center study for spinal cord injury database (JSSCI-DB). RESULTS: Data were collected from 139 individuals at the acute stage and 164 individuals at discharge. In the comparison of utility score by severity in acute stage and discharge, G3 was significantly higher in discharge (0.325 versus 0.580). Utility scores by degree of severity were significantly higher in group G4 than those of G1, G2, and G3 at the acute stage. Utility scores at discharge were significantly higher in groups G3 and G4 than in G1, and there was a significant difference between groups G4 and G2. CONCLUSIONS: At each stage, the utility scores of group G4 were significantly higher than those of groups G1 and G2. Altogether, the utility scores for hospitalized patients with traumatic SCI that were indicated in this study will serve as basic data that can be used while performing spinal regeneration medical procedures in the future.

Comparison of human papillomavirus genotyping and cytology triage, COMPACT Study: Design, methods and baseline results in 14 642 women.

Although cytology-based screening programs have significantly reduced mortality and morbidity from cervical cancer, the global consensus is that primary human papillomavirus (HPV) testing for cervical screening increases detection of high-grade cervical intraepithelial neoplasia (CIN) and invasive cancer. However, the optimal triage strategy for HPV-positive women to avoid over-referral to colposcopy may be setting specific. As Japan requires data that have been generated domestically to modify screening guidelines, we conducted a 3-year prospective study, COMparison of HPV genotyping And Cytology Triage (COMPACT), to evaluate the potential role of HPV16/18 partial genotyping and cytology for primary HPV screening. In total, 14 642 women aged 20 to 69 years undergoing routine screening at 3 centers in Hokkaido were enrolled. Conventional cytology and HPV testing were carried out. Women with abnormal cytology or HPV16/18 positivity underwent colposcopy. Those with 12 other high-risk (hr) HPV types underwent repeat cytology after 6 months. Primary study endpoints were detection of high-grade cervical disease defined as CIN2/CIN3 or greater as determined by consensus pathology. Prevalence of cytological abnormalities was 2.4%. hrHPV, HPV 16, and HPV 18 were detected in 4.6%, 0.9%, and 0.3% of women, respectively. HPV16/18 were detected in all (8/8) invasive cervical cancers and in all (2/2) adenocarcinomas in situ. Both cytological abnormalities and hrHPV positivity declined with increasing age. This is the first Japanese study to investigate the role of partial genotyping and cytology in an HPV-based screening program. Results should help policy-makers develop guidelines for future cervical screening programs and management of cervical abnormalities based on HPV genotype.

A chimeric protein of aluminum-activated malate transporter generated from wheat and Arabidopsis shows enhanced response to trivalent cations.

TaALMT1 from wheat (Triticum aestivum) and AtALMT1 from Arabidopsis thaliana encode aluminum (Al)-activated malate transporters, which confer acid-soil tolerance by releasing malate from roots. Chimeric proteins from TaALMT1 and AtALMT1 (Ta::At, At::Ta) were previously analyzed in Xenopus laevis oocytes. Those studies showed that Al could activate malate efflux from the Ta::At chimera but not from At::Ta. Here, functions of TaALMT1, AtALMT1 and the chimeric protein Ta::At were compared in cultured tobacco BY-2 cells. We focused on the sensitivity and specificity of their activation by trivalent cations. The activation of malate efflux by Al was at least two-fold greater in the chimera than the native proteins. All proteins were also activated by lanthanides (erbium, ytterbium, gadolinium, and lanthanum), but the chimera again released more malate than TaALMT1 or AtALMT1. In Xenopus oocytes, Al, ytterbium, and erbium activated inward currents from the native TaALMT1 and the chimeric protein, but gadolinium only activated currents from the chimera. Lanthanum inhibited currents from both proteins. These results demonstrated that function of the chimera protein was altered compared to the native proteins and was more responsive to a range of trivalent cations when expressed in plant cells.

A Dicarboxylate Transporter, LjALMT4, Mainly Expressed in Nodules of Lotus japonicus.

Legume plants can establish symbiosis with soil bacteria called rhizobia to obtain nitrogen as a nutrient directly from atmospheric N2 via symbiotic nitrogen fixation. Legumes and rhizobia form nodules, symbiotic organs in which fixed-nitrogen and photosynthetic products are exchanged between rhizobia and plant cells. The photosynthetic products supplied to rhizobia are thought to be dicarboxylates but little is known about the movement of dicarboxylates in the nodules. In terms of dicarboxylate transporters, an aluminum-activated malate transporter (ALMT) family is a strong candidate responsible for the membrane transport of carboxylates in nodules. Among the seven ALMT genes in the Lotus japonicus genome, only one, LjALMT4, shows a high expression in the nodules. LjALMT4 showed transport activity in a Xenopus oocyte system, with LjALMT4 mediating the efflux of dicarboxylates including malate, succinate, and fumarate, but not tricarboxylates such as citrate. LjALMT4 also mediated the influx of several inorganic anions. Organ-specific gene expression analysis showed LjALMT4 mRNA mainly in the parenchyma cells of nodule vascular bundles. These results suggest that LjALMT4 may not be involved in the direct supply of dicarboxylates to rhizobia in infected cells but is responsible for supplying malate as well as several anions necessary for symbiotic nitrogen fixation, via nodule vasculatures.

Two Members of the Aluminum-Activated Malate Transporter Family, SlALMT4 and SlALMT5, are Expressed during Fruit Development, and the Overexpression of SlALMT5 Alters Organic Acid Contents in Seeds in Tomato (Solanum lycopersicum).

The aluminum-activated malate transporter (ALMT) family of proteins transports malate and/or inorganic anions across plant membranes. To demonstrate the possible role of ALMT genes in tomato fruit development, we focused on SlALMT4 and SlALMT5, the two major genes expressed during fruit development. Predicted proteins were classified into clade 2 of the family, many members of which localize to endomembranes. Tissue-specific gene expression was determined using transgenic tomato expressing the ß-glucuronidase reporter gene controlled by their own promoters. Both the genes were expressed in vascular bundles connecting to developing seeds in fruit and in the embryo of mature seeds. Further, SlALMT5 was expressed in embryo in developing seeds in fruit. Subcellular localization of both proteins to the endoplasmic reticulum (ER) was established by transiently expressing the green fluorescent protein fusions in plant protoplasts. SlALMT5 probably localized to other endomembranes as well. Localization of SlALMT5 to the ER was also confirmed by immunoblot analysis. The transport function of both SlALMT proteins was investigated electrophysiologically in Xenopus oocytes. SlALMT5 transported malate and inorganic anions such as nitrate and chloride, but not citrate. SlALMT4 also transported malate, but the results were less consistent perhaps because it did not localize strongly to the plasma membrane. To elucidate the physiological role of SlALMT5 further, we overexpressed SlALMT5 in tomato. Compared with the wild type, overexpressors exhibited higher malate and citrate contents in mature seeds, but not in fruit. We conclude that the malate transport function of SlALMT5 expressed in developing fruit influences the organic acid contents in mature seeds.

Human papillomavirus type 16 sequence variation in concurrent vulvar and penile carcinoma in a married couple.

We encountered an elderly married couple with concurrent vulvar and penile carcinoma with an Asian variant of human papillomavirus type 16. Asian variants might have an elevated risk of concurrent external genital carcinomas of a male and a female, and analysis of human papillomavirus variants might be important to understand the mechanism of carcinogenesis.

A domain-based approach for analyzing the function of aluminum-activated malate transporters from wheat (Triticum aestivum) and Arabidopsis thaliana in Xenopus oocytes.

Wheat and Arabidopsis plants respond to aluminum (Al) ions by releasing malate from their root apices via Al-activated malate transporter. Malate anions bind with the toxic Al ions and contribute to the Al tolerance of these species. The genes encoding the transporters in wheat and Arabidopsis, TaALMT1 and AtALMT1, respectively, were expressed in Xenopus laevis oocytes and characterized electrophysiologically using the two-electrode voltage clamp system. The Al-activated currents generated by malate efflux were detected for TaALMT1 but not for AtALMT1. Chimeric proteins were generated by swapping the N- and C-terminal halves of TaALMT1 and AtALMT1 (Ta::At and At::Ta). When these chimeras were characterized in oocytes, Al-activated malate efflux was detected for the Ta::At chimera but not for At::Ta, suggesting that the N-terminal half of TaALMT1 is necessary for function in oocytes. An additional chimera, Ta(48)::At, generated by swapping 17 residues from the N-terminus of AtALMT1 with the equivalent 48 residues from TaALMT1, was sufficient to support transport activity. This 48 residue region includes a helical region with a putative transmembrane domain which is absent in AtALMT1. The deletion of this domain from Ta(48)::At led to the complete loss of transport activity. Furthermore, truncations and a deletion at the C-terminal end of TaALMT1 indicated that a putative helical structure in this region was also required for transport function. This study provides insights into the structure-function relationships of Al-activated ALMT proteins by identifying specific domains on the N- and C-termini of TaALMT1 that are critical for basal transport function and Al responsiveness in oocytes.

Incidence risk of cervical intraepithelial neoplasia 3 or more severe lesions is a function of human papillomavirus genotypes and severity of cytological and histological abnormalities in adult Japanese women.

We examined incidence probabilities of cervical intraepithelial neoplasia 3 (CIN3) or more severe lesions (CIN3+) in 1,467 adult Japanese women with abnormal cytology in relation to seven common human papillomavirus (HPV) infections (16/18/31/33/35/52/58) between April 2000 and March 2008. Sixty-seven patients with multiple HPV infection were excluded from the risk factor analysis. Incidence of CIN3+ in 1,400 patients including 68 with ASCUS, 969 with low grade squamous intraepithelial lesion (LSIL), 132 with HSIL without histology-proven CIN2 (HSIL/CIN2(-)) and 231 with HSIL with histology-proven CIN2 (HSIL/CIN2(+)) was investigated. In both high grade squamous intraepithelial lesion (HSIL)/CIN2(-) and HSIL/CIN2(+), HPV16/18/33 was associated with a significantly earlier and higher incidence of CIN3+ than HPV31/35/52/58 (p = 0.049 and p = 0.0060, respectively). This association was also observed in LSIL (p = 0.0002). The 1-year cumulative incidence rate (CIR) of CIN3+ in HSIL/CIN2(-) and HSIL/CIN2(+) according to HPV genotypes (16/18/33 vs. 31/35/52/58) were 27.1% vs. 7.5% and 46.6% vs. 19.2%, respectively. In contrast, progression of HSIL/CIN2(+) to CIN3+ was infrequent when HPV DNA was undetected: 0% of 1-year CIR and 8.1% of 5-year CIR. All cervical cancer occurred in HSIL cases of seven high-risk HPVs (11/198) but not in cases of other HPV or undetectable/negative-HPV (0/165) (p = 0.0013). In conclusion, incidence of CIN3+ depends on HPV genotypes, severity of cytological abnormalities and histology of CIN2. HSIL/CIN2(+) associated with HPV16/18/33 may justify early therapeutic intervention, while HSIL/CIN2(-) harboring these HPV genotypes needs close observation to detect incidence of CIN3+. A therapeutic intervention is not indicated for CIN2 without HPV DNA.

Segregated and alternately stacked donor/acceptor nanodomains in tubular morphology tailored with zinc porphyrin-C60 amphiphilic dyads: clear geometrical effects on photoconduction.

Amphiphilic zinc porphyrin (P(Zn); electron donor, D)-fullerene (C(60); electron acceptor, A) dyads 2 and 3, bearing an identical hydrophilic wedge with triethylene glycol chains but different linkers between the P(Zn) and C(60) units, self-assemble into nanotubes with essentially different dimensional and geometrical features from one another. The nanotube from dyad 2 with an ester linker consists of a bilayer wall formed with coaxially segregated D and A nanodomains along the tube axis (coaxial D-A heterojunction), thereby displaying explicit photoconductivity with ambipolar carrier transport properties. In contrast, the nanotube from dyad 3 with a rigid arylacetylene linker consists of a monolayer wall with an alternate geometry of D/A stacking, resulting in poor photoconducting outputs. Such a geometrical difference also significantly affects the photovoltaic properties.

Inhibitory effects of methylglyoxal on light-induced stomatal opening and inward K+ channel activity in Arabidopsis.

Methylglyoxal (MG) is a reactive aldehyde derived by glycolysis. In Arabidopsis, MG inhibited light-induced stomatal opening in a dose-dependent manner. It significantly inhibited both inward-rectifying potassium (K(in)) channels in guard-cell protoplasts and an Arabidopsis K(in) channel, KAT1, heterologously expressed in Xenopus oocytes. Thus it appears that MG inhibition of stomatal opening involves MG inhibition of K(+) influx into guard cells.

Sorption of Cs+ and Eu3+ ions onto sedimentary rock in the presence of gamma-irradiated humic acid.

The influence of humic acid (HA) and its radiological degradation on the sorption of Cs+ and Eu3+ by sedimentary rock (obtained from the Horonobe Underground Research Laboratory in Japan) was investigated to understand the sorption process of metal ions and humic substances. Aldrich HA solution was gamma-irradiated assuming a strong radiation from a highly radioactive waste to be disposed of in deep geological formations. Batch sorption experiments were performed to evaluate the effect of gamma-irradiated HA on the sorption of Cs+ and Eu3+ ions. The addition of non-irradiated HA weakened the Eu sorption because of the lower sorption of the negatively charged Eu-HA complexes compared with free Eu ions. The sorption of Cs ions was barely affected by the presence of HA and its gamma irradiation. The concentration ratio of metal complexed and non-complexed species in the solid and liquid phases was evaluated by sequential filtration and chemical equilibrium calculations. The ratios were low in both phases for Cs and supported the minimal contribution of HA to Cs sorption. However, the concentration ratio for Eu3+ in the liquid phase was high, indicating that the complexing ability of HA to Eu3+ was higher than that of HA to Cs+.

An extracellular hydrophilic carboxy-terminal domain regulates the activity of TaALMT1, the aluminum-activated malate transport protein of wheat.

Al³+ -resistant cultivars of wheat (Triticum aestivum L.) release malate through the Al³+ -activated anion transport protein Triticum aestivum aluminum-activated malate transporter 1 (TaALMT1). Expression of TaALMT1 in Xenopus oocytes and tobacco suspension cells enhances the basal transport activity (inward and outward currents present in the absence of external Al³+, and generates the same Al³+ -activated currents (reflecting the Al³+-dependent transport function) as observed in wheat cells. We investigated the amino acid residues involved in this Al³+-dependent transport activity by generating a series of mutations to the TaALMT1 protein. We targeted the acidic residues on the hydrophilic C-terminal domain of TaALMT1 and changed them to uncharged residues by site-directed mutagenesis. These mutant proteins were expressed in Xenopus oocytes and their transport activity was measured before and after Al³+ addition. Three mutations (E274Q, D275N and E284Q) abolished the Al³+-activated transport activity without affecting the basal transport activity. Truncation of the hydrophilic C-terminal domain abolished both basal and Al³+-activated transport activities. Al³+-dependent transport activity was recovered by fusing the N-terminal region of TaALMT1 with the C-terminal region of AtALMT1, a homolog from Arabidopsis. These findings demonstrate that the extracellular C-terminal domain is required for both basal and Al³+-dependent TaALMT1 activity. Furthermore, we identified three acidic amino acids within this domain that are specifically required for the activation of transport function by external Al³+.

The multiple origins of aluminium resistance in hexaploid wheat include Aegilops tauschii and more recent cis mutations to TaALMT1.

Acid soils limit plant production worldwide because their high concentrations of soluble aluminium cations (Al(3+) ) inhibit root growth. Major food crops such as wheat (Triticum aestivum L.) have evolved mechanisms to resist Al(3+) toxicity, thus enabling wider distribution. The origins of Al(3+) resistance in wheat are perplexing because all progenitors of this hexaploid species are reportedly sensitive to Al(3+) stress. The large genotypic variation for Al(3+) resistance in wheat is largely controlled by expression of an anion channel, TaALMT1, which releases malate anions from the root apices. A current hypothesis proposes that the malate anions protect this sensitive growth zone by binding to Al(3+) in the apoplasm. We investigated the evolution of this trait in wheat, and demonstrated that it has multiple independent origins that enhance Al(3+) resistance by increasing TaALMT1 expression. One origin is likely to be Aegilops tauschii while other origins occurred more recently from a series of cis mutations that have generated tandemly repeated elements in the TaALMT1 promoter. We generated transgenic plants to directly compare these promoter alleles and demonstrate that the tandemly repeated elements act to enhance gene expression. This study provides an example from higher eukaryotes in which perfect tandem repeats are linked with transcriptional regulation and phenotypic change in the context of evolutionary adaptation to a major abiotic stress.

Gamma-irradiation-induced molecular-weight distribution and complexation affinity of humic acid with Cs+, Sr2+, and Eu3.

Solutions of humic acid (HA) were irradiated with 0, 1, 5, 10, 50, and 100 kGy of gamma irradiation using a 60Co source. The non-irradiated and irradiated HA molecules were fractionated by ultrafiltration into four categories: > 100, 50-100, 10-50, and < 10 kDa. Total organic carbon measurements and potentiometric titration analysis suggested that (1) some gamma-irradiated HA molecules were degraded into smaller molecules and (2) radiolytic degradation caused phenolic -OH became the predominant functional group in the small molecular-weight fractions of HA. The effect of absorbed dose of gamma rays on the distributions of Cs+, Sr2+, and Eu3+ ions in the molecular-weight fractions of the metal-HA systems was examined to discuss the complexation affinity. The metal ions were distributed in the smaller molecular-weight fractions at different doses, which corresponded to the degradation of HA molecules. For a predetermined absorbed dose, Cs+ ions did not change the molecular-weight distribution of the total organic carbon content of the degraded HA molecules. Conversely, the Sr2+ and Eu3+ ions redistributed organic carbon toward the larger molecular-weight fractions.