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PubMedDate not supplied

Career transition from clinician to academician: responsibilities and reflections.

Being an educator is just as much an art and a science as is being a clinician. This article describes the faculty role and its basic responsibilities for occupational therapy practitioners who are considering the transition to academic educator positions. The faculty role has unique characteristics. Differentiating therapy activities from academic activities is an essential part of a career transition from clinician to academician. This article also describes the various features of the academic context and its impact on individual performance, how to assess readiness for the faculty role, and the typical application process.

Career Mobility↗

PubMed2006

Sorption of Sb(III) and Sb(V) to goethite: influence on Sb(III) oxidation and mobilization.

Antimony is an element of growing interest for a variety of industrial applications, even though Sb compounds are classified as priority pollutants by the Environmental Protection Agency of the United States. Iron (Fe) hydroxides appear to be important sorbents for Sb in soils and sediments, but mineral surfaces can also catalyze oxidation processes and may thus mobilize Sb. The aim of this study was to investigate whether goethite immobilizes Sb by sorption or whether Sb(III) adsorbed on goethite is oxidized and then released. The sorption of both Sb(III) and Sb(V) on goethite was studied in 0.01 and 0.1 M KClO4 M solutions as a function of pH and Sb concentration. To monitor oxidation processes Sb species were measured in solution and in the solid phase. The results show that both Sb(III) and Sb(V) form inner-sphere surface complexes at the goethite surface. Antimony(III) strongly adsorbs on goethite over a wide pH range (3-12), whereas maximum Sb(V) adsorption is found below pH 7. At higher ionic strength, the desorption of Sb(V) is shifted to lower pH values, most likely due to the formation of ion pairs KSb(OH)6 degrees. The sorption data of Sb(V) can be fitted by the modified triple-layer surface complexation model. Within 7 days, Sb(III) adsorbed on goethite is partly oxidized at pH 3, 5.9 and 9.7. The weak pH-dependence of the rate coefficients suggests that adsorbed Sb(III) is oxidized by 02 and that the coordination of Sb(III) to the surface increases the electron density of the Sb atom, which enhances the oxidation process. At pH values below pH 7, the oxidation of Sb(III) did not mobilize Sb within 35 days, while 30% of adsorbed Sb(III) was released into the solution at pH 9.9 within the same time. The adsorption of Sb(III) on Fe hydroxides over a wide pH range may be a major pathway for the oxidation and release of Sb(V).

Adsorption↗

PubMed2001

Combining G-CSF with a blockade of adhesion strongly improves the reconstitutive capacity of mobilized hematopoietic progenitor cells.

OBJECTIVE: Mobilization of hematopoietic progenitor cells is achieved mainly by application of growth factors and, more recently, by blockade of adhesion. In this report, we describe the advantages of a combined treatment with granulocyte colony-stimulating factor (G-CSF) and anti-VLA4 (CD49d)/anti-CD44 as compared to treatment with the individual components. MATERIALS AND METHODS: Mobilization by intravenous injection of anti-CD44, anti-VLA4, or G-CSF was controlled in spleen and bone marrow with regard to frequencies of multipotential colony-forming unit (C-CFU), marrow repopulating ability, long-term reconstitution, recovery of myelopoiesis, and regain of immunocompetence. RESULTS: Mobilization by anti-CD44 had a strong effect on expansion of early progenitor cells in the bone marrow, while the recovery in the spleen was poor. In anti-CD49d-mobilized noncommitted and committed progenitors, progenitor expansion was less pronounced, but settlement in the spleen was quite efficient. Thus, anti-CD44 and anti-CD49d differently influenced mobilization. Accordingly, mobilization and recovery after transfer were improved by combining anti-CD44 with anti-CD49d treatment. Mobilization by G-CSF was most efficient with respect to recovery of progenitor cells in the spleen. However, when transferring G-CSF-mobilized cells, regain of immunocompetence was strongly delayed. This disadvantage could be overridden when progenitor cells were mobilized via blockade of adhesion and when expansion of these mobilized progenitor cells was supported by low-dose G-CSF only during the last 24 hours before transfer. CONCLUSION: Mobilization of pluripotent progenitor cells via antibody blockade of CD44 or CD49d or via G-CSF relies on distinct mechanisms. Therefore, the reconstitutive capacity of a transplant can be significantly improved by mobilization regimens combining antibody with low-dose G-CSF treatment.

Animals↗

PubMed2006

Application of liquid chromatography-electrospray ionisation mass spectrometry for determination of dietary folates: effects of buffer nature and mobile phase composition on sensitivity and selectivity.

A sensitive and reliable liquid chromatography-mass spectrometry (LC-MS) method to determine dietary folates was developed and validated. Folates were detected and quantified using positive electrospray ionisation (ESI) with selective ion monitoring of protonated ions [M+H]+. The effects of buffer nature and mobile phase composition on separation, peak shape and intensity of MS signal were investigated. The acidic-basic properties of folates were successfully used to predict possible ionisation patterns, but they were not sufficient to predict the intensity of MS signal and the proportion of different ionisation products, which indicated that other parameters, such as gas phase acidity/basicity of analytes and ion evaporation mechanisms might be important. The use of aqueous acetic acid as volatile buffer was found to be preferable compared to formic acid due to considerable gain in intensity of MS signal for all folate forms studied. Limits of quantifications were 0.3 ng/mL for 5-methyltetrahydrofolate and 0.6 ng/mL for tetrahydrofolate, 10-formylfolic acid, 5-formyltetrahydrofolate and folic acid when using 20 microL injection. For 10-formylfolic acid, 5-formyltetrahydrofolate and folic acid the MS detection was found to be superior over commonly used fluorescence and UV detection in terms of selectivity and sensitivity. The method was successfully applied to analysis of folates in baker's yeast.

Animals↗

PubMed1993

Recombinant human granulocyte colony-stimulating factor can mobilize sufficient amounts of peripheral blood stem cells in healthy volunteers for allogeneic transplantation.

Peripheral blood stem cells (PBSC) are a good source for bone marrow reconstitution after intensive chemotherapy. The ability to transplant PBSC between allogeneic subjects would be a key step forward in the application of this procedure. For this purpose, we examined the mobilization and recovery of PBSC in healthy volunteers who were given recombinant human granulocyte colony-stimulating factor (G-CSF). Three informed healthy volunteers were injected with G-CSF subcutaneously at a dose of 2.5 micrograms/kg for 6 successive days and at 5.0 micrograms/kg for the following 4 days. The concentration of PBSC was assessed daily by CFU-GM and BFU-E assays, both of which peaked on the sixth to seventh day of G-CSF administration. Comparison between colony assays and hematological parameters revealed that flow cytometry analysis of CD34+ cells by mononuclear cell gating is a rapid and convenient method to quantify mobilized stem cells. The maximum numbers of CFU-GM were 432, 665, and 1386 colonies/ml blood. It is calculated that sufficient amounts of stem cells for transplantation (at least 1.0 x 10(5) CFU-GM/kg) could be obtained by leukapheresis of 5 to 201 blood when the peak was attained. This trial confirmed the feasibility of allogeneic transplantation using PBSC from healthy volunteers who have received G-CSF.

Adult↗

PubMed1996

Allogeneic peripheral blood progenitor cells: current status and future directions.

Increasing use is being made of mobilized peripheral blood as a source of hematopoietic stem and progenitor cells for transplantation. Initially, these efforts were focused on autologous applications. However, many centers are now using cells derived from normal donors mobilized with recombinant hematopoietic growth factors for allogeneic transplantation. This article reviews the key issues associated with the use of these cells for hematologic reconstitution and summarizes important recent developments in the field.

Blood Cell Count↗

PubMedDate not supplied

Lead phytoextraction from contaminated soil with high-biomass plant species.

In this study, cabbage [Brassica rapa L. subsp. chinensis (L.) Hanelt cv. Xinza No 1], mung bean [Vigna radiata (L.) R. Wilczek var. radiata cv. VC-3762], and wheat (Triticum aestivum L. cv. Altas 66) were grown in Pb-contaminated soils. Application of ethylenediaminetetraacetic acid (EDTA) (3.0 mmol of EDTA/kg soil) to the soil significantly increased the concentrations of Pb in the shoots and roots of all the plants. Lead concentrations in the cabbage shoots reached 5010 and 4620 mg/kg dry matter on Days 7 and 14 after EDTA application, respectively. EDTA was the best in solubilizing soil-bound Pb and enhancing Pb accumulation in the cabbage shoots among various chelates (EDTA, diethylenetriaminepentaacetic acid [DTPA], hydroxyethylenediaminetriacetic acid [HEDTA], nitrilotriacetic acid [NTA], and citric acid). Results of the sequential chemical extraction of soil samples showed that the Pb concentrations in the carbonate-specifically adsorbed and Fe-Mn oxide phases were significantly decreased after EDTA treatment. The results indicated that EDTA solubilized Pb mainly from these two phases in the soil. The relative efficiency of EDTA enhancing Pb accumulation in shoots (defined as the ratio of shoot Pb concentration to EDTA concentration applied) was highest when 1.5 or 3.0 mmol EDTA/kg soil was used. Application of EDTA in three separate doses was most effective in enhancing the accumulation of Pb in cabbage shoots and decreased mobility of Pb in soil compared with one- and two-dose application methods. This approach could help to minimize the amount of chelate applied in the field and to reduce the potential risk of soluble Pb movement into ground water.

Biodegradation, Environmental↗

PubMed2002

Application of a dual channel peroneal nerve stimulator in a patient with a "central" drop foot.

Dropped foot is a common mobility problem amongst patients after a cerebro vascular accident. The condition arises from paresis of the muscles that control the foot movement during the swing phase of gait. If the abnormal movement is not compensated for, it results in a significant decrease in the mobility and hence quality of life. Compensation for the drop foot can be achieved through the application of functional electrical stimulation. To date, in the clinical environment, the stimulation has been applied through electrodes placed on the skin over the common peroneal nerve, and using a single channel implant device. It is well known that with these techniques it is difficult to establish a balanced response of the foot. An implantable dual channel system for stimulation of the deep and superficial peroneal nerve has now been developed for patients with a drop foot following a stroke. By stimulation of the two branches of the common peroneal nerve separately it is possible to achieve a precisely balanced dorsal flexion and eversion of the foot. Stimulation occurs via small bipolar electrodes which are placed subepineural. After successful tests on animals we have now started the two channel peroneal nerve stimulator implantation in patients. The preliminary results of the first implants are presented.

Cerebrovascular Disorders↗

PubMed1980

Thermodynamic nonideality and the dependence of partition coefficient upon solute concentration in exclusion chromatography. Application to self-associating and non-self-associating solutes. Application to hemoglobin.

The theory of partition of macromolecular solute between mobile and stationary phases under highly nonideal conditions is reexamined. Expressions are derived for the dependence of the partition coefficient of a non-self-associating solute, and the weight average partition coefficient of a dimerizing solute, upon the total concentration of solute in the mobile phase. These expressions are based upon a treatment of nonideality in the stationary phase which is more realistic than that proposed earlier [L.W. Nichol, R.J. Siezin and D.J. Winzor, Biophys. Chem. 9 (1979) 17]. It is found that the chromatographic data on oxyhemoglobin in the above paper may be accommodated by the present theory without invoking self-association.

Chromatography, Gel↗

PubMed1995

Modeling the electrophoresis of rigid polyions: application to lysozyme.

An algorithm is developed to determine the electrophoretic mobility of a rigid polyion modeled as a low dielectric volume element of arbitrary shape containing an arbitrary charge distribution. The solvent is modeled as a high dielectric continuum with salt distributed according to the linearized Poisson Boltzmann equation. Account is also taken of a Stern layer that separates the molecular surface and the surface of hydrodynamic shear, or Stern surface. Relaxation of the ion atmosphere because of the presence of the external field is ignored. The electrostatic and hydrodynamic problems are both solved by boundary element methods. The procedure is first applied to spherical polyions containing monopolar, dipolar, and quadrupolar charge distributions, and calculated mobilities are found to be in excellent agreement with the theory of Yoon and Kim. It is then applied to lysozyme by using models that account for the detailed shape and charge distribution of the enzyme. For reasonable choices of the molecular and Stern surfaces, calculated and experimental mobilities are found to be in fair agreement with each other. However, if a pH independent Stern layer (or, equivalently, translational diffusion constant, Dt) is assumed, the calculated mobilities exhibit a stronger pH dependence than is observed experimentally. A small increase in Dt with increasing pH could correct this discrepancy.

Algorithms↗

PubMed2002

Rituximab in vivo purging is safe and effective in combination with CD34-positive selected autologous stem cell transplantation for salvage therapy in B-NHL.

The purpose of this study was to evaluate feasibility and efficacy of Rituximab included into a sequential salvage protocol for CD20(+) B-NHL in relapse or induction failure. Twenty-seven patients with CD20(+) B-NHL in relapse or induction failure received Rituximab combined with DexaBEAM (R-DexaBEAM) for stem cell mobilization. Additional ex vivo selection of CD34-positive cells was performed using the CliniMacs device. Two doses of Rituximab were included in the high-dose therapy regimen (HDT). R-DexaBEAM was well tolerated and 26 of 27 patients mobilized sufficient numbers of CD34(+) blood stem cells. Application of R-DexaBEAM resulted in significant depletion of peripheral B cells. No treatment-related deaths occurred after HDT and all patients showed stable engraftment of hematopoesis. Combined immunodeficiency was observed post HDT and eight patients developed CMV antigenemia. Remission rate post HDT was 96% (CR, 24/26; PR, 1/26). Overall and progression-free survival (PFS) at 16 months post HDT (range 6-27) is 95% and 77%, respectively. With regard to histology, PFS was 71% in aggressive lymphoma (n = 11), 74% in indolent FCL (n = 10) and 100% in MCL (n = 5). The treatment protocol has proven feasible, with high purging efficiency and encouraging remission rates.

Adult↗

PubMed2001

[Role and functional spectrum of HPTLC in a hospital pharmaceutical quality control program].

As part of the development of a quality assurance program (QAP), a high performance thin layer chromatography (HPTLC) analysis unit was installed in the pharmacy department at Gustave-Roussy. The HPTLC-CAMAG consists of: 1) an HPTLC-Vario development chamber for optimization of the mobile phases; 2) TLC Sampler III automated sample applicators; 3) solid teflon migration chambers, i.e., horizontal tanks that enable separation to be carried out either in sandwich or in saturation mode; 4) a TLC Scanner 3 densitometer controlled by CATS 4 software; and 5) a Pentium MMX 233 MHz personal computer with an external backup unit. HPTLC quantitative and qualitative analysis has now reached a remarkably high level of development and performance. The samples (aqueous or non-aqueous solutions) that are to be processed are automatically applied by spraying (50-300 nl) in calibrated bands of a few mm (with up to 64 3-mm bands per 10 x 20 cm plate) on high-performance stationary phases and of wide technological diversity. The chromatogram is obtained in 10 min, and run over a migration pathway of 5-6 cm. The plates are read by absorption-reflection or fluorescence-reflection at an ad hoc wavelength (190-800 nm), then the peak areas which have been scanned are calculated by the trapezoid method. The calibration curves are generated by Michaelis-Menten non-linear regression, and validated by internal quality control. The analytical yield is high, i.e., up to 50 assays and 250 determinations per day. HPTLC analysis covers a wide functional range, and can be used in the following ways: 1) as a teaching tool for separative analysis and GLP; 2) it is an invaluable method for the optimization of mobile phases and for the determination of absorption spectra and absorption maxima, with a view to developing HPLC methods in complex matrices; 3) it provides major support for post-production quality control of prescribed hospital preparations of all types, e.g., those connected with parenteral nutrition, chemotherapy, synthetic narcotic analgesia; and it can also be used for dry dosage analysis; 4) it is useful in pharmaceutical assessment, e.g., in studies on the physico-chemical characteristics of various substances, such as their identity, purity, concentration, stability and compatibility, particularly with regard to generic products; 5) it can contribute to monitoring the safety of medical apparatus and equipment via the analysis of container-content interactions; 6) it provides a qualification system for personnel and procedures for within- and between-center validation of GMP. Setting up such an HPTLC quality control unit requires a basic investment of about 0.9 MF or 70,000 US dollars for a cost of no more than 10 F or 1.5 US dollars (including tax) per routine assay. After 18 months in operation and 16,500 assays, the HPTLC analysis unit has become one of the mainstays of the Gustave-Roussy QAP.

Chromatography, High Pressure Liquid↗

PubMed2006

Accumulation and chemical fractionation of heavy metals in andisols after a different, 6-year fertilization management.

GOAL, SCOPE AND BACKGROUND: Andisols are widespread in Japan and have some special properties such as high anion exchange capacity, low bulk density, and high organic matter content, which might influence the accumulation or chemical fractionation of heavy metals. However, few such data exist in Japanese andisols. The primary objective of this study was to investigate the distribution and chemical fractions of Cu, Zn, Ni, and Cr in the soil profiles and subsequently to assess their potential environmental hazard. MATERIALS AND METHODS: Soil samples were taken from a field experiment conducted on Japanese andisols, which had received either swine compost or chemical fertilizers for 6 years. Concentrations of Cu, Zn, Ni, and Cr were determined for all of the obtained extract solutions by ICP-AES. RESULTS AND DISCUSSION: Considerably higher total concentrations of Cu and Zn were observed in the top 20 cm layer of the compost-amended soil, relative to the unfertilized soil, while chemical fertilizers had little effect. Application of the swine compost increased the concentrations of Cu and Zn, but not Ni and Cr, in all fractions in the top 20 cm layer. The greatest increase in the organically bound fraction (OM) Cu and dilute acid-exchangeable fraction (DAEXCH) Zn was observed. This suggests that Cu and Zn are potentially bioavailable and mobile in the andisol profiles after 6-year consecutive applications of the swine compost. On the other hand, distribution of Cu, Zn, Ni and Cr among various soil fractions was generally unaffected by chemical fertilizers. CONCLUSIONS: We observed that 6-year consecutive applications of the swine compost led to an increase in total metals of Cu and Zn, as well as their all-chemical fractions, in the top 20 cm soil layers. Potential hazard of heavy metals, especially of Cu and Zn, as a result of the use of swine compost on andisols, must be taken into account. RECOMMENDATIONS AND OUTLOOK: The long-term effect of the accumulation of heavy metals, particularly Cu and Zn, in various plant tissues and soils, as well as their potential risk to surface water via runoff and groundwater via leaching, needs to be carefully considered. Further investigations in the long-term experiments are therefore necessary.

Agriculture↗

PubMed2005

[A new complex approaches for the identification of Listeria isolated during production of fermented sausages].

Distribution L. monocytogenes and other Listeria spp. in raw meat and during manufacturing of fermented meat products is investigated. The high contamination of raw materials and semi finished foods--in 36.5% of samples, ready-to-eat sausages--31.8% by Listeria spp. is established. Detection L. monocytogenes in 9.7% cases from the surfaces of equipment indicates the intensive circulation of listeriosis agents on meat plants. For identification 49 isolated strains the approach providing application of most informative for L. monocytogenes phenotypical tests (mobility, ability to haemolysis, presence of specific lecithinase) and assay based on PCR of DNA sites, coding phospholipase, factors of invasion and citotoxicity is used. Efficiency of this circuit is confirmed with positive results PCR with species-specific for L. monocytogenes primers to genes PIcA and ActA only at strains, having lecithinase and haemolysis activity. Application of the given approach has allowed to reduce in three times number of the cultures initially identified as L. monocytogenes on a complex of biochemical tests.

Colony Count, Microbial↗

PubMed2001

Total urogenital sinus mobilization in the repair of cloacal anomalies and congenital adrenal hyperplasia.

PURPOSE: Urogenital sinus mobilization has facilitated markedly the vaginal reconstruction in cases of cloacal anomalies. Application of the same technique in cases of congenital adrenal hyperplasia has resulted in cosmetic and functional improvement. METHODS: Total urogenital sinus mobilization was used as a part of the repair in 9 patients: 6 with congenital adrenal hyperplasia (4 high and 2 mid vaginal confluence), and 3 with cloacal anomalies; sinus mobilization to the level of the symphesis pubis allowed the vagina to reach the perineum in all cases. Their age ranged from 6 to 8 months, and follow-up ranged from 6 months to 2 years. In the former group, the mobilized sinus was split dorsally and used as an anterior vaginal flap. Cases of cloaca needed weekly dilatation early postoperatively. RESULTS: All patients are below 3 years of age, so urinary control assessment is not yet objective; however, all mothers reported dry intervals. Examination 6 months postoperatively showed wide vagina and excellent cosmetic appearance in all cases. CONCLUSIONS: Total urogenital mobilization provides an easier way for vaginal reconstruction. The improved cosmetic appearance and the absence of vaginal stenosis provided by this technique is a major advantage in the management of these difficult surgical situations.

Adrenal Hyperplasia, Congenital↗

PubMed2007

Development of a homogeneous calcium mobilization assay for high throughput screening of mas-related gene receptor agonists.

AIM: To develop homogeneous calcium mobilization assay for high-throughput screening (HTS) of mas-related gene (Mrg) receptor agonists. METHODS: CHO-K1 cells stably expressing the full-length MrgD receptor and a calcium-sensitive dye were used to develop an HTS assay based on intracellular calcium influx. This method was applied to large-scale screening of a library containing 8000 synthetic compounds and natural product extracts. cAMP measurements were carried out to verify the bioactivities of the hits found by the calcium mobilization assay. Similar approaches were also employed in the identification of the MrgA1 receptor agonists following HTS of 16,000 samples. RESULTS: EC(50) values of the positive control compounds (beta-alanine for MrgD receptor and dynorphin A for MrgA1 receptor) determined by the calcium mobilization assay were consistent with those reported in the literature, and the Z' factors were 0.65 and 0.50 for MrgD and MrgA1 receptor assay, respectively. About 31 compounds for the MrgD receptor and 48 compounds for the MrgA1 receptor showing > or =20% of the maximal agonist activities found in the controls were initially identified as hits. Secondary screening confirmed that 2 compounds for each receptor possessed specific agonist activities. Intracellular cAMP level measurements indicated that the 2 confirmed hits displayed the functionality of the MrgD receptor agonists. CONCLUSION: A series of validation studies demonstrated that the homogeneous calcium mobilization assay developed was highly efficient, amenable to automation and a robust tool to screen potential MrgD and MrgA1 receptor agonists. Its application may be expanded to other G-protein coupled receptors that mobilize calcium influx upon activation.

Animals↗

PubMed2004

Reevaluation of bone marrow-derived cells as a source for hepatocyte regeneration.

We have investigated the contribution of intrasplenic bone marrow transplants or in vivo mobilized hematopoietic stem cells to the formation of hepatocytes in normal and injured liver. Direct intrasplenic injections of bone marrow mononuclear cells (5 x 10(5) cells), Scal+/lin- hematopoietic stem cells (5 x 10(3)) cells, and highly purified "side population" hematopoietic stem cells (5 x 10(3)) derived from enhanced green fluorescent protein (EGFP)-transgenic mice [C57Bl/6-TgN(ActbEGFP)1Osb] were performed in normal C57Bl/6 mice (n = 6) and in C57Bl/6 mice following two thirds hepatectomy (n = 8). To test the effect of mobilized stem cells on transdifferentiation, C57Bl/6 mice (n = 12) were lethally irradiated and reconstituted with EGFP-positive bone marrow mononuclear cells in a second series of experiments. Eight to 12 weeks after bone marrow transplantation a subset of mice (n = 3 in each group) received either rhG-CSF for hematopoietic stem cell mobilization, rhG-CSF combined with an intraperitoneal application of carbon tetrachloride (CCl4) as hepatocyte regeneration stimulus, or CCl4 alone. All mice were completely perfused with PBS to remove circulating nonorgan cells for analyses 4 weeks later. Liver as well as heart, intestine, spleen, and kidney tissue was analyzed for the presence of EGFP-transgenic cells. In 100 sections (2.3 x 10(7) cells) of any recipient mouse no EGFP-positive hepatocytes were detected either by analysis of native EGFP fluorescence or by immunofluorescence analysis with anti-EGFP and antidipeptidyl peptidase (DPP) IV antibodies. EGFP-transgenic cells resembling heart, kidney, or intestinal cells could also not be proven. The results demonstrate that there is little or no contribution of bone marrow-derived cells to the regeneration of normal and injured liver in the animal models used. Thus, potential therapeutic prospects of hematopoietic stem cell therapy for liver disease have to be critically reassessed.

Animals↗

PubMed1985

Molecular dynamics in protein-single stranded DNA complexes. Two distinct nucleoside mobilities, in poly(deoxythymidylic acid)-poly-L-lysine complexes.

Stoichiometric amounts of poly-L-lysine were added to site-specifically spin labeled single stranded nucleic acids and the resulting complexes analyzed by electron spin resonance spectroscopy (ESR). The nucleic acids were spin labeled to different extents and with labels of varying tether length. The ESR data are used to determine nucleoside dynamics and some structural features in these complexes. It is concluded that two distinct base mobilities exist in the complexes; one set is characterized by a mean correlation time tau -R = 2 ns, and the other one by a tau -R greater than or equal to 50 ns. A model is proposed which suggests that a poly-L-lys single stranded nucleic acid complex consists of low mobility segments flanked by more mobile bases. An interesting feature of the proposed model is its applicability to explain ESR data of single strand binding protein-spin labeled nucleic acid complexes, which can also be interpreted in terms of two distinct nucleoside mobility states. It is hypothesized that this phenomenon could be of biological significance for the release of protein ligands from a protein-nucleic acid complex.

Binding Sites↗