Seven new species of Eimeria Schneider, 1875 (Apicomplexa: Eimeriidae) from colubrid snakes of Guatemala and a discussion of what to call ellipsoid tetrasporocystic, dizoic coccidia of reptiles

During a survey of Guatemalan herpetofauna in the summers of 1998–2000, 29 presumed new species of Eimeria Schneider, 1875 were found, seven of which have a distinct elongate-ellipsoidal shape (L/W ratio ≥ 1.7) and are described herein. Six of the seven new species are similar in oöcyst length, width and L/W ratio and sporocyst length, width and L/W ratio, lack a micropyle, oöcyst residuum, Stieda body, sub- and parastieda bodies, have a polar granule and sporocyst residuum, and their sporocysts appear to have dehiscence sutures. The seventh is slightly smaller and has sporocysts with a Stieda body. The new species are: E. coniophanes n. sp – whose sporulated oöcysts from Coniophanes fissidens are 29.2×14.9 (27–31×13–16) m, with sporocysts m; E. coniophis n. sp. –from Conophis lineatus are 32.0×16.5 (30–34×14–18) m, with sporocysts m; E. dryomarchoni n. sp. – from Drymarchon corais are 32.2×17.7 (31–34×17–19) m, with sporocysts m; E. leptophis n. sp. – from Leptophis mexicanus are 29.5×17.0 (28–31×16–18) m, with sporocysts m; E. oxybelis n. sp. – from Oxybelis aeneus are 31.8×16.5 (29–33×15–18) m, with sporocysts m; and E. scaphiodontophis n. sp. – from Scaphiodontophis annulatus are 30.0×15.3 (28–33×14–16) m, with sporocysts m. Sporulated oöcysts of E. siboni n. sp. from Sibon nebulata are 24.3×14.2 (21–27×13–16) m, with sporocysts m and with a Stieda body. We conclude that until all aspects of each life-cycle are known, it is prudent at this time to name all tetrasporocystic dizoic coccidia from snakes as members of Eimeria rather than place some of them in Choleoeimeria Paperna & Landsberg, 1989.     

Use of isotopic signatures to assess the food web in a tropical shallow marine ecosystem of Southeastern Brazil

A dual isotope approach was used to assess the relative importance of terrestrial vegetation detritus and other primary producers in the trophic web of Flamengo Sound (Ubatuba, SP), SE Brazil, surrounded by the Atlantic Rain Forest. Primary producers showed distinct C signatures and the observed values suggest that little terrestrial or bulk sediment organic matter enter the food web of the sound. Suspended particulate organic matter (POM, supports the bulk of the consumers, with some contribution by macroalgae . Consumers C values ranged from −17.4 to . At least three trophic levels were detectable in the food web. The N value of POM was , while that of sediment and detritus was . The N values of suspension feeding benthic invertebrates were 8.2–, deposit feeders 8.3–, and carnivores 10.7–. Values for fishes were for detritivore, 11.4– for benthic feeders, 12.4– for zooplanktivores, and for piscivores/benthic invertebrate feeders. Squid mean value was . There is a reasonable agreement between feeding habits information from the literature and N values from this study. In the sound, the first and second trophic steps seem to be about 1– higher than those of similar organisms studied in temperate waters and this may reflect an input of allochtonous anthropogenic nitrogen enriched in ¹⁵N from human activities.     

Three-dimensional quantitative structure-activity relationship (3D-QSAR) studies of various benzodiazepine analogues of γ-secretase inhibitors

A 3D QSAR analysis has been performed on a series of 67 benzodiazepine analogues reported as γ-secretase inhibitors using molecular field analysis (MFA), with G/PLS to predict steric and electrostatic molecular field interaction for the activity. The MFA study was carried out using a training set of 54 compounds. The predictive ability of model developed was assessed using a test set of 13 compounds ( as high as 0.729). The analyzed MFA model has demonstrated a good fit, having r² value of 0.858 and cross validated coefficient, value as 0.790. The analysis of the best MFA model provided insight into possible modification of the molecules for better activity.   Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Leaching losses of inorganic N and DOC following repeated drying and wetting of a spruce forest soil

Forest soils are frequently subjected to dry–wet cycles, but little is known about the effects of repeated drying and wetting and wetting intensity on fluxes of , and DOC. Here, undisturbed soil columns consisting of organic horizons (O columns) and organic horizons plus mineral soil (O + M columns) from a mature Norway spruce stand at the Fichtelgebirge; Germany, were repeatedly desiccated and subsequently wetted by applying different amounts of water (8, 20 and 50 mm day⁻¹) during the initial wetting phase. The constantly moist controls were not desiccated and received 4 mm day⁻¹ during the entire wetting periods. Cumulative inorganic N fluxes of the control were 12.4 g N m⁻² (O columns) and 11.4 g N m⁻² (O + M columns) over 225 days. Repeated drying and wetting reduced cumulative and fluxes of the O columns by 47–60 and 76–85%, respectively. Increasing (0.6–1.1 g N m⁻²) and decreasing fluxes (7.6–9.6 g N m⁻²) indicate a reduction in net nitrification in the O + M columns. The negative effect of dry–wet cycles was attributed to reduced net N mineralisation during both the desiccation and wetting periods. The soils subjected to dry–wet cycles were considerably drier at the final wetting period, suggesting that hydrophobicity of soil organic matter may persist for weeks or even months. Based on results from this study and from the literature we hypothesise that N mineralisation is mostly constrained by hydrophobicity in spruce forests during the growing season. Wetting intensity did mostly not alter N and DOC concentrations and fluxes. Mean DOC concentrations increased by the treatment from 45 mg l⁻¹ to 61–77 mg l⁻¹ in the O tlsbba columns and from 12 mg l⁻¹ to 21–25 mg l⁻¹ in the O + M columns. Spectroscopic properties of DOC from the O columns markedly differed within each wetting period, pointing to enhanced release of rather easily decomposable substrates in the initial wetting phases and the release of more hardly decomposable substrates in the final wetting phases. Our results suggest a small additional DOC input from organic horizons to the mineral soil owing to drying and wetting.     

Effects of common soil anions and pH on the uptake and accumulation of perchlorate in lettuce

A mechanistic understanding of perchlorate () entry into plants is important for establishing the human health risk associated with consumption of contaminated produce and for assessing the effectiveness of phytoremediation. To determine whether common soil anions affect uptake and accumulation in higher plants, a series of competition experiments using lettuce (Lactuca sativa L.) were conducted between (50 nM) and (4–12 mM), (1–10 mM), or Cl⁻ (5–15 mM) in hydroponic solution. The effects of (0–5 mM) and pH (5.5–7.5) on uptake were also examined. Increasing in solution significantly reduced the amount of taken up by green leaf, butter head, and crisphead lettuces. Sulfate and Cl⁻ had no significant effects on uptake in lettuce over the concentrations tested. Increasing pH significantly reduced the amount of taken up by crisphead and green leaf lettuces, whereas increasing significantly reduced uptake in butter head lettuce. The inhibition by across all lettuce genotypes suggests that may share an ion carrier with , and the decrease in uptake with increasing pH or provides macroscopic evidence for cotransport across the plasma membrane.     

Soil algal communities inhabiting zinc and lead mine spoils

Algal communities inhabiting four calamine mine spoils differing in time since cessation of exploitation and loaded with high concentrations of zinc (20,284–61,599 μg g⁻¹ soil DW), lead (2,620–3,885 μg g⁻¹ DW) and cadmium (104–232 μg g⁻¹ DW) were studied. In dump soils of slightly alkaline pH (7.28–7.52) and low nutrient (, , ) concentrations, chlorophyll a content ranged from 0.41 to 2.27 μg g⁻¹ soil DW. In total, 23 algal species were recorded. Chlorophyta were the dominant taxonomic group (42–55% of all identified species) followed by Cyanobacteria (28–36%) and Heterokontophyta (13–21%). The highest species richness (18) was observed in the oldest dump (120 years old) with natural succession, while in younger dumps it was lower (11–15). Total algal abundance ranged between 5.5 and 19.1 × 10² ind. g⁻¹ soil DW, and values of Margalef’s diversity indices (1.59–2.25) were low. These results may suggest that both high concentrations of heavy metals and low nutrient content influenced the algal communities in all the dumps studied. The differences in algal microflora observed between tailing dumps may indicate that habitat quality improved with time and that algae isolated from Zn/Pb-loaded soils may be Zn/Pb-resistant ecotypes of ubiquitous species.     

Influence of inbreeding depression on a lake population of Nymphoides peltata after restoration from the soil seed bank

The negative effects of inbreeding depression on fragmented small populations are likely to be expressed more strongly after restoration efforts if regeneration processes have been highly restricted in degraded habitats. We examined the potential influences of inbreeding depression on a population of Nymphoides peltata (Menyanthaceae) restored from the remnant soil seed bank. A hand-pollination experiment demonstrated self-compatibility of a single remaining homostyle genet and significant inbreeding depression in selfed progeny, especially in parameters related to seedling growth (–0.6 for biomass, and –0.4 for relative growth rate). Our genetic analysis indicated that the presumed number of parents contributing to the current soil seed bank was only 2–8 genets and that a single sib-family dominated at each of three sampling sites. The results also showed that the selfed progeny of the homostyle genet were overwhelmingly dominant at two sites (86.8 and 94.7%). As a result, the growth performance of the seed bank seedlings was significantly reduced, to a level as low as that of the selfed progeny. Active restoration efforts to minimize the negative effects of the genetic bottleneck and continuous monitoring based on genetic and demographic study are recommended.     

Set theory formulation of the model-free problem and the diffusion seeded model-free paradigm

Model-free analysis of NMR relaxation data, which describes the motion of individual atoms, is a problem intricately linked to the Brownian rotational diffusion of the macromolecule. The diffusion tensor parameters strongly influence the optimisation of the various model-free models and the subsequent model selection between them. Finding the optimal model of the dynamics of the system among the numerous diffusion and model-free models is hence quite complex. Using set theory, the entirety of this global problem has been encapsulated by the universal set Ll, and its resolution mathematically formulated as the universal solution Ll. Ever since the original Lipari and Szabo papers the model-free dynamics of a molecule has most often been solved by initially estimating the diffusion tensor. The model-free models which depend on the diffusion parameter values are then optimised and the best model is chosen to represent the dynamics of the residue. Finally, the global model of all diffusion and model-free parameters is optimised. These steps are repeated until convergence. For simplicity this approach to Ll will be labelled the diffusion seeded model-free paradigm. Although this technique suffers from a number of problems many have been solved. All aspects of the diffusion seeded paradigm and its consequences, together with a few alternatives to the paradigm, will be reviewed through the use of set notation.     

Estimating the Accuracy of Protein Structures using Residual Dipolar Couplings

It has been commonly recognized that residual dipolar coupling data provide a measure of quality for protein structures. To quantify this observation, a database of 100 single-domain proteins has been compiled where each protein was represented by two independently solved structures. Backbone ¹H–¹⁵N dipolar couplings were simulated for the target structures and then fitted to the model structures. The fits were characterized by an R-factor which was corrected for the effects of non-uniform distribution of dipolar vectors on a unit sphere. The analyses show that favorable values virtually guarantee high accuracy of the model structure (where accuracy is defined as the backbone coordinate rms deviation). On the other hand, unfavorable values do not necessarily suggest low accuracy. Based on the simulated data, a simple empirical formula is proposed to estimate the accuracy of protein structures. The method is illustrated with a number of examples, including PDZ2 domain of human phosphatase hPTP1E. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.     

Chloroform degradation by butane-grown cells of Rhodococcus aetherovorans BCP1

The ability of a Rhodococcus aetherovorans strain, BCP1, to grow on butane and to degrade chloroform in the 0–633 μM range (0–75.5 mg l⁻¹) via aerobic cometabolism was investigated by means of resting-cell assays. BCP1 degraded chloroform with a complete mineralization of the organic Cl. The resulting butane and chloroform maximum specific degradation rates were equal to 118 and 22 μmol , respectively. Butane inhibition on chloroform degradation was satisfactorily interpreted by means of a model of competitive inhibition, with an inhibition constant equal to 38 % of the estimated butane half-saturation constant, whereas chloroform (at 11 μM) did not inhibit butane utilization. Acetylene (1,720 μM) induced an almost complete inactivation of the degradation of both butane and chloroform, indicating that the studied cometabolic process is mediated by a monooxygenase enzyme. BCP1 proved capable of degrading vinyl chloride and 1,1,2-trichloroethane, but not 1,2-trans-dichloroethylene. BCP1 could grow on the intermediates of the most common butane metabolic pathways and on the aliphatic hydrocarbons from ethane to n-heptane. After growth on n-hexane, it was able to deplete chloroform (13 μM) with a degradation rate higher than that obtained, at the same chloroform concentration, after growth on butane.Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Theoretical study of AlH(2+)n (n=1-7) dications

The structures and stability of 1–7 dications were calculated at the ab initio MP2/aug-cc-pVTZ level of theory. The dications AlH²⁺ 1 and 2 were characterized to be unstable thermodynamically. However, these and the stable dications, 3–7 have considerable kinetic barriers for deprotonation. Each of the structures 3–7 contains one or more two-electron three-center (2e–3c) bonds. Aluminum atoms of these dications carry most of the positive charges, as indicated by NBO charge calculations.Dedicated to Professor Dr. Paul von Ragué Schleyer on the occasion of his 75th birthday     

Factors affecting denitrification in agricultural headwater streams in Northeast Ohio,USA

As a result of increased anthropogenic nitrogen (N) loading in surface waters of agricultural watersheds, there is enhanced interest to understand and quantify N removal mechanisms. Denitrification, an important N removal mechanism in aquatic systems, may contribute to reducing N pollution in agricultural headwater streams. However, the key factors controlling this process in lotic systems remain unclear. The objective of our study was to examine the factors regulating rates of denitrification in the sediments of agricultural headwater streams in the mid-western USA. Denitrification rates were variable among streams and treatments (<0.1–28.0 μg N g AFDM⁻¹ h⁻¹) and on average, were higher than those reported for similar headwater streams. Carbon quantity and quality, and pH had no effect on denitrification, while temperature and nitrate ( ) concentrations had a positive effect on rates of denitrification. Specifically, controlled denitrification following Michaelis-Menten kinetics. We calculated a value of k_m (1.0 mg -N L^-1) that was comparable to other studies in aquatic sediments but was well below the median in-stream concentrations (5.2–17.4 mg -N L⁻¹) observed at the study sites. Despite high rates of denitrification, this removal mechanism is most likely saturated in the agricultural headwater streams we examined, suggesting that these systems are not effective at removing in-stream N. Handling editor: D. Ryder     

RBE of quasi-monoenergetic 60 MeV neutron radiation for induction of dicentric chromosomes in human lymphocytes

The production of dicentric chromosomes in human lymphocytes by high-energy neutron radiation was studied using a quasi-monoenergetic 60 MeV neutron beam. The average yield coefficient of the linear dose–response relationship for dicentric chromosomes was measured to be (0.146±0.016) Gy⁻¹. This confirms our earlier observations that above 400 keV, the yield of dicentric chromosomes decreases with increasing neutron energy. Using the linear-quadratic dose–response relationship for dicentric chromosomes established in blood of the same donor for ⁶⁰Co γ-rays as a reference radiation, an average maximum low-dose RBE (RBE_M) of 14±4 for 60 MeV quasi-monoenergetic neutrons with a dose-weighted average energy of 41.0 MeV is obtained. A correction procedure was applied, to account for the low-energy continuum of the quasi-monoenergetic spectral neutron distribution, and the yield coefficient α for 60 MeV neutrons was determined from the measured average yield coefficient . For α, a value of (0.115±0.026) Gy⁻¹ was obtained corresponding to an RBE_M of 11±4. The present experiments extend earlier investigations with monoenergetic neutrons to higher energies.     

Sources of variability in spotted owl population growth rate: testing predictions using long-term mark–recapture data

For long-lived iteroparous vertebrates that annually produce few young, life history theory predicts that reproductive output (R) and juvenile survival should influence temporal variation in population growth rate (λ) more than adult survival does. We examined this general prediction using 15 years of mark–recapture data from a population of California spotted owls (Strix occidentalis occidentalis). We found that survival of individuals ≥1 year old (ϕ) exhibited much less temporal variability , where CV is coefficient of variation, than R and that R was strongly influenced by environmental stochasticity. Although λ was most sensitive ( ; log-transformed sensitivity) to ϕ and much less sensitive to either R or juvenile survival (survival rate of owls from fledging to 1 year old; ), we estimated that R contributed as much as ϕ to the observed annual variability in λ. The contribution of juvenile survival to variability in λ was proportional to its These results are consistent with the hypothesis that natural selection may have favored the evolution of longevity in spotted owls as a strategy to increase the probability of experiencing favorable years for reproduction. Our finding that annual weather patterns that most affected R (temperature and precipitation during incubation) and ϕ (conditions during winter related to the Southern Oscillation Index) were equally good at explaining temporal variability in λ supports the conclusion that R and ϕ were equally responsible for variability in λ. Although currently accepted conservation measures for spotted owl populations attempt to enhance survival, our results indicated that conservation measures that target R may be as successful, as long as actions do not reduce ϕ.     

Process Optimization,Characterization and Pharmacokinetic Evaluation in Rats of Ursodeoxycholic Acid–Phospholipid Complex

The purpose of this research was to study whether the bioavailability of ursodeoxycholic acid could be improved by administering ursodeoxycholic acid–phospholipid complex (UDCA–PLC) orally to rats. A central composite design approach was used for process optimization in order to obtain the acceptable UDCA–PLC. The physicochemical properties of the complex obtained by optimal parameters were investigated by means of scanning electron microscopy and X-ray diffraction. The pharmacokinetic parameters and bioavailability studies were conducted in rats of UDCA after oral administration of UDCA–PLC and UDCA tablet. Multiple linear regression analysis for process optimization revealed that the acceptable UDCA–PLC was obtained wherein the optimal values of X ₁, X ₂ and X ₃ were 3, 60°C and 3 h, respectively. The XRD studies of UDCA–PLC obtained by the optimal parameters demonstrated that UDCA and phospholipids in the UDCA–PLC were combined by non-covalent bonds, not form new compounds. But pharmacokinetic parameters of the complex in rats were T _max 1.6 h, C _max 0.1346 μg/ml, 11.437 μg·h/ml, respectively. The relative bioavailability of UDCA of UDCA–PLC was increased by 241%,compared with the reference ursodeoxycholic acid tablet.     

Quantifying Lipari–Szabo modelfree parameters from 13CO NMR relaxation experiments

It is proposed to obtain effective Lipari–Szabo order parameters and local correlation times for relaxation vectors of protein ¹³CO nuclei by carrying out a ¹³CO-R₁ auto relaxation experiment, a transverse CSA/dipolar cross correlation and a transverse ¹³CO CSA/¹³CO–¹⁵N CSA/dipolar cross correlation experiment. Given the global rotational correlation time from ¹⁵N relaxation experiments, a new program COMFORD (CO-Modelfree Fitting Of Relaxation Data) is presented to fit the ¹³CO data to an effective order parameter , an effective local correlation time and the orientation of the CSA tensor with respect to the molecular frame. It is shown that the effective is least sensitive to rotational fluctuations about an imaginary axis and most sensitive to rotational fluctuations about an imaginary axis parallel to the NH bond direction. As such, the information is fully complementary to the ¹⁵N relaxation order parameter, which is least sensitive to fluctuations about the NH axis and most sensitive to fluctuations about the axis. The new paradigm is applied on data of Ca²⁺ saturated Calmodulin, and on available literature data for Ubiquitin. Our data indicate that the order parameters rapport on slower, and sometimes different, motions than the ¹⁵N relaxation order parameters. The CO local correlation times correlate well with the calmodulin’s secondary structure. Electronic Supplementary Material Supplementary material is available to authorized users in the online version of this article at .     

Population parameters and harvest risks for polar bears (<Emphasis Type="Italic">Ursus maritimus</Emphasis>) of Kane Basin,Canada and Greenland

We estimated demographic parameters and current harvest risks for a population of polar bears (Ursus maritimus Phipps) inhabiting northern Smith Sound and Kane Basin, Canada and Greenland. Our demographic analysis included a detailed assessment of age- and sex-specific survival and recruitment from 141 marked polar bears, using information contained within the standing age distribution of captures and mark-recapture analysis. Total survival rates for females were: 0.374 ± 0.180 (cubs), 0.686 ± 0.157 (ages 1–4), and 0.967 ± 0.043 (ages 5+). Mean litter size was 1.67 ± 0.08 cubs. Females did not reproduce until at least age 6, which is late compared to other populations of polar bears. The model-averaged, mark–recapture estimate of mean abundance (±1 SE) for years 1994–1997 was 164 ± 35 bears. We incorporated demographic parameters and their variances into a harvest risk analysis (i.e., a stochastic, harvested population viability analysis, PVA). Results suggest that polar bears in the region were severely over-harvested during the mark–recapture interval (1992–1997). The current status of the population is unknown.     

Phosphorus concentration in sediment, water and tissues of␣three submerged macrophytes of Myall Lake, Australia

Phosphorus content in sediment, water and tissues of three macrophyte species growing in Myall Lake, Australia were studied from January to November, 2004. The sites investigated were North–West (NW), North–East (NE), South–West (SW) bays and Central deep area of the lake (CL). The objective of this study was to investigate how total phosphorus (TP) in plant tissues relate to phosphorus pools and the role played by the aquatic macrophyte species under investigation in phosphorus recycling in the lake. Of the four investigated sites of the lake, TP in plant tissues were significantly higher in North–West and South–West bays compared to the rest. Najas marina had significantly higher TP content (e.g., 1.55 and 1.44 mg/g dw.; P < 0.05) for NW and SW respectively, than the other two species. N. marina is a rooted macrophyte while charophytes (C. fibrosa and Nitella hyalina) are pseudo-rooted macrophytes. Total phosphorus in the sediment and water column were significantly higher in Central deep area of the lake compared to the other three bays (P < 0.05, n 5). Soluble reactive phosphorus (SRP) and total dissolved phosphorus (TDP) in sediment pore water correlated significantly with phosphorus content in the tissue of N. marina ( ; ) as well as TP in sediment (␣ and ). Using the two-compartmental uptake model, it was observed that, sediment was the main compartment through which Ni. hyalina obtained phosphorus while for the other two species, water column was the uptake route for the phosphorus. These correlations suggest that, water column and sediments are important pathways for phosphorus uptake in plants.     

Serum selenium concentrations in ovarian cancer patients using a simplified fluorimetric procedure

The serum selenium (Se) concentrations were determined to be 105.6±15.6 μg/L ( ) and 116.7±18.4 μg/L ( ) for the ovarian cancer patients and the control subjects in Singapore, respectively (p<0.0065). When we separated the patients into three age groups, namely <30, 30–50, and >50 yr, the ovarian cancer patients showed significantly lower mean serum Se levels than the control subjects for the 30–50-yr age group only. However, when the analysis of variance was used to evaluate the data, the values indicated that the age of the subject did not significantly affect the serum Se level. Our findings suggest that there is an inverse relationship between serum Se concentration and the incidence of human ovarian cancer. A modified simple fluorimetric method for the determination of serum Se concentration is described. The procedure, with a sensitivity limit of 5 μg/L and percentage recoveries of 96.2–100.7%, requires only 0.2 mL of serum sample.     

Mobility of NH bonds in DNA-binding protein HU of shape Bacillus stearothermophilus from reduced spectral density mapping analysis at multiple NMR fields

The dynamics of the backbone NH bonds of protein HU from Bacillus stearothermophilus (HUBst) have been characterized using measurements of cross-relaxation, longitudinal and transverse relaxation rates at 11.7, 14.1 and 17.6 T. Linear regression of the values with the squared Larmor frequency _N ² has revealed global exchange processes, which contributed on the order of 0.5–5.0 s^-1to the transverse relaxation rate. Subsequently, the experimental values were corrected for these exchange contributions. A reduced spectral density mapping procedure has been employed with the experimental relaxation rates and seven values of the spectral density function J() have been extracted. These spectral densities have been fitted within the framework of the model-free approach. The densities agree well with an axially symmetric rotational diffusion tensor with a diffusion anisotropy D_/D_ of 1.15, indicating that the flexible arms of HUBst do not significantly contribute to the rotational diffusion. The overall correlation time is 8.9 ± 0.6 ns/rad. The fast internal motions of most of the NH bonds in the core display order parameters ranging between 0.74 and 0.83 and internal correlation times between 1 and 20 ps. For the residues in the DNA-binding -arms, an extended version of the model function has been used. The slow internal motions show correlation times of 1–2 ns. The concomitant order parameters (0.3–0.6) are lower than those observed on the fast time scale, indicating that the flexibility of the -arms is mainly determined by the slower internal motions. A substantial decrease of the generalized order parameters in the -arms starting at residues Arg⁵⁵ and Ser⁷⁴, opposite on both strands of the -ribbon arms, has been explained as a hinge motion. A comparison of the order parameters for free and DNA-bound protein has demonstrated that the slow hinge motions largely disappear when HU binds DNA.