SEARCH · PubMed Health

Results for “IRON, RADIOACTIVE”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,063 records · Page 59Linked to original sources

PubMed1978

Effect of intrauterine growth on erythropoiesis.

Erythropoietic activity, as reflected in the reticulocyte count and the incorporation of 59Fe into red cells, was studied in relation to intrauterine growth of rabbit fetuses during the last third of the period of gestation. Radioiron (10 microci) was administered by i.v. injection into the mothers and placental transfer to the fetuses. The fetuses were extracted after 48 hours. The amount of radioiron received by each individual fetus was determined by whole body counting. Radioactivity in red cells was determined and calculated as a percentage of the dose received. From day 21 to day 31 of gestation, the hemoglobin concentration increased by a factor of 1.5, from 8 to 12.2 g/100 ml, while the body mass increased by a factor of 7, from 6.6 to 47.5 g. During the same period the rate of growth declined from 45 to 20% in 24 hours. This was paralleled by a drop in 59Fe incorporation from 35 to 12% and in the reticulocyte count from 85 to 14.5%. It is concluded that the rate of erythropoiesis in fetal life is largely controlled by the rate of growth and the corresponding increase in hemoglobin mass.

Animals↗

PubMed2006

Preliminary study of physico-chemical treatment options for hospital wastewater.

Hospital effluents are loaded with pathogenic microorganisms, partially metabolized pharmaceutical substances, radioactive elements, and other toxic substances. Such effluents if not treated properly can damage the natural environment and create a biological imbalance. This paper points out the areas of concern for hospital wastewater disposal and reports the findings of a limited physico-chemical study of treatment options for hospital effluents conducted at Christian Medical College and Hospital, Vellore, Tamil Nadu. The effluent collected was checked for conventional parameters and subjected to coagulation experiments. The raw and settled effluents were coagulated with FeCl(3), filtered and disinfected. Physico-chemical treatment seems to be an attractive option for the cost-effective disposal of hospital effluents. The results of this study call for further detailed study in this area.

Biodegradation, Environmental↗

PubMed1989

32P-postlabeling assay for carcinogen-DNA adducts and other dna modifications.

32P-postlabeling analysis is a recently developed, highly sensitive method for the detection and measurement of covalent DNA adducts. Since the method does not require radioactive carcinogens, it is suitable for DNA of humans exposed to environmental or occupational genotoxicants. The basic procedure entails the enzymatic incorporation of 32P-label into enzymatic digestion products of DNA, the chromatographic separation and autoradiographic detection of the 32P-labeled digestion products and their quantitation by scintillation counting. Since only microgram amounts of DNA are required, the assay is well suited for the analysis of DNA lesions whenever only limited amounts of cells or tissue may be available. Various versions of the assay have been described affording different sensitivities of adduct detection. Under optimal conditions, one aromatic or bulky/hydrophobic adduct in 10(8) - 10(10) nucleotides can be detected and measured (this corresponds to 0.0003 - 0.03 fmol adduct/microgram DNA or 0.1 - 10 nmol adduct/mol DNA-P). The assay has been successfully applied to a variety of mutagenic (genotoxic) as well as non-mutagenic carcinogens. Among the latter are estrogens and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In addition, the assay detects age-dependent DNA modifications (I-compounds) in animals that have not been knowingly exposed to mutagens/carcinogens. In humans, the 32P-postlabeling assay has been applied to cigarette smokers, iron foundry workers and coke oven workers. Estimation of total aromatic adduct levels in exposed individuals gave values of 1 adduct in 10(6) - 10(8) DNA nucleotides. These values are similar to the total levels of persistent adducts in tissues of animals after exposure to initiating or carcinogenic doses of authentic aromatic geno-toxicants.

Aging↗

PubMed2006

Laboratory analyses of 60Co2+, 65Zn2+ and (55+59)Fe3+ radiocations uptake by Lemna minor.

The living Lemna minor vascular plant and two different sorbents obtained by chemical treatment of this plant were tested to study the removal process of 60Co2+, 65Zn2+ and (55+59)Fe3+ from low radioactive wastewaters. The most effective sorbent was the protonated biomass, indicating the decisive contribution of the complexation process in the assembly of the uptake mechanisms. The uptake performance of the biosorbent obtained from the L. minor can be increased with approximately 20% by treatment with 0.1 N HNO3. Concerning the metabolically active mechanism, it can be notice the slow elimination of 65Zn2+ and the continuously increase of (55+59)Fe3+ uptake degree. The Na2CO3 generated in situ in systems participates to a double exchange reaction with the metallic cations during the uptake. 60Co2+, 65Zn2+ and (55+59)Fe3+ radiocations prefer for coordination N-donor ligands at the expense O-donors ones.

Araceae↗

PubMed1973

Studies on red cell aplasia. V. Presence of erythroblast cytotoxicity in G-globulin fraction of plasma.

The marrow cells of a patient with pure red cell aplasia markedly increased their rate of heme synthesis when they were freed from the host environment and were incubated in vitro. When the red cell aplasia was treated with cyclophosphamide and prednisone, marrow cell incorporation of (59)Fe into heme in vitro increased several weeks before a reticulocytosis was apparent, and was the earliest effect noted. The plasma gammaG-globulins of this patient inhibited heme synthesis by normal marrow cells or the patient's own marrow cells obtained after remission of the disease. Since the inhibition of heme synthesis could be the result of damage to erythroblasts, the patient's posttreatment marrow cells or normal marrow cells were labeled with (59)Fe and were then incubated with the patient's pretreatment, treatment, and posttreatment gammaG-globulins as well as normal gammaG-globulins. At the end of this incubation the supernatant and cells were separated and counted. Heme was extracted and also was counted. Treatment of the cells with the patient's pretreatment gammaG-globulins resulted in a release of 40% of the radioactive heme from the cells. This represented the loss of radioactive hemoglobin and was an index of erythroblast cytotoxicity. A progressive disappearance of the cytotoxic factor in the gammaG-globulins occurred in the 3 wk period preceding the onset of reticulocytes in the patient's blood. Posttreatment and normal gammaG-globulins did not produce this effect and increased injury of red cells and lymphocytes was not produced by the patient's pretreatment gammaG-globulins. These studies demonstrate a method for measuring erythroblast cytoxicity and show that red cell aplasia is associated with gammaG-globulins that specifically damage erythroblasts. Whether interference with new erythroblast development also occurs and contributes to the inhibition of heme synthesis has not yet been ascertained.

Anemia, Aplastic↗

PubMed1990

Differential effect of pH on the density and volume of rat reticulocytes and erythrocytes. Relevance to their fractionation by centrifugation.

Rats were injected with 59Fe-ferrous citrate and bled thereafter at different times (16 h to 49 d). This gave rise to red cell populations in which cells corresponding in age to the time elapsed between injection and bleeding were labeled. The anticoagulant used was either acid-citrate-dextrose (ACD) with a pH adjusted to 7.3 or ACD (pH 5.1). Final pH of the collected blood was about 7.2-7.4 in the former case and 6.4-6.7 in the latter. Red cells were then centrifuged (5) and approximately 7-10% of the packed cells from the top and 7-10% from the bottom of the cell column collected. When reticulocytes are the predominant labeled red cell population, as in blood obtained for about 24 h after isotope injection, a fractionation of these cells and mature erythrocytes is in evidence only when blood is collected at the higher pH. Thus, at pH 7.2-7.4 ratios of specific radioactivities of cells in top fraction/cells in an unfractionated sample are about 3, whereas at pH 6.4-6.7, the analogous ratios are 1 or less. These differences in specific activity ratios, as a function of pH at collection, virtually disappear after about 4 d following isotope injection. The lower pH is known to increase the volume and decrease the density of mature red blood cells. The marked effect of pH on cellular fractionation could be correlated with the smaller change in rat reticulocyte density and volume in acid medium. At pH 6.4-6.7, the densities of mature erythrocytes and reticulocytes are so close that their physical separation by centrifugation is not feasible.

Animals↗

PubMed1971

Loss of haem in rat liver caused by the porphyrogenic agent 2-allyl-2-isopropylacetamide.

1. The effect of a single dose of 2-allyl-2-isopropylacetamide on the cytochrome P-450 concentration in rat liver microsomal fraction was studied. The drug caused a rapid loss of cytochrome P-450 followed by a gradual increase to above the normal concentration. 2. The loss of cytochrome P-450 was accompanied by a loss of microsomal haem and by a brown-green discoloration of the microsomal fraction suggesting that a change in the chemical constitution of the lost haem had taken place. Direct evidence for this was obtained by prelabelling the liver haems with radioactive 5-aminolaevulate: the drug caused a loss of radioactivity from the haem with an increase of radioactivity in a fraction containing certain un-identified green pigments. 3. Evidence was obtained by a dual-isotopic procedure that rapidly turning-over haem(s) may be preferentially affected. 4. The loss of cytochrome P-450 as well as the loss of microsomal haem and the discoloration of the microsomal fraction were more intense in animals pretreated with phenobarbitone and were much less evident when compound SKF 525-A (2-diethylaminoethyl 3,3-diphenylpropylacetate) was given before 2-allyl-2-isopropylacetamide, suggesting that the activity of the drug-metabolizing enzymes may be involved in these effects. 5. The relevance of the destruction of liver haem to the increased activity of 5-aminolaevulate synthetase caused by 2-allyl-2-isopropylacetamide is discussed.

Acetamides↗

PubMed1990

Quantitative autoradiographic assessment of 55Fe-RBC distribution in rat brain.

A simple in vivo technique of labeling erythrocytes (RBCs) with 55Fe was developed for quantitative autoradiography (QAR). This procedure involved injecting 5-6 ml of [55Fe]ferrous citrate solution (1 mCi/ml) intraperitoneally into donor rats. The number of labeled RBCs reached a maximum at around 7 days and declined very slowly thereafter. Labeled RBCs were harvested from donor rats and used for RBC volume measurement in awake rats. Brain radioactivity was assayed by QAR, which yielded spatial resolution of greater than 50 microns. Tight nearly irreversible binding of 55Fe to RBCs was found in vivo and in vitro. More than 99.5% of the 55Fe in the blood of donor rats was bound to RBCs. Because of this, labeled blood can be taken from donors and injected into recipients without further preparation. The tissue absorption of 55Fe emissions was the same in gray and white matter. Microvascular RBC volumes measured with 55Fe-labeled RBCs agreed with those assayed with 51Cr-labeled RBCs for many, but not all, brain areas. In conclusion, 55Fe-RBCs can be readily prepared by this technique and accurately quantitated in brain tissue by QAR.

Animals↗

PubMed1991

Molybdenum requirement for translocation of dimethyl sulfoxide reductase to the periplasmic space in a photodenitrifier, Rhodobacter sphaeroides f. sp. denitrificans.

Translocation of dimethyl sulfoxide (DMSO) reductase to the periplasmic space was studied in vivo with a photodenitrifier, Rhodobacter sphaeroides f. sp. denitrificans, using immunoblotting analysis and radioactive labeling. A polypeptide with an apparent molecular mass about 2,000 Da higher than that of DMSO reductase accumulated during induction of the reductase with DMSO. An uncoupler, carbonyl cyanide-m-chlorophenylhydrazone, inhibited the processing of the polypeptide after cells had been radioactively pulse-labeled with [35S]methionine. These results indicated that the higher-molecular-mass polypeptide was the precursor form of DMSO reductase. The precursor form accumulated in either the cytoplasm or the membrane, whereas the mature form accumulated in the periplasmic space. The membrane-bound precursor was sensitive to proteinase K treatment from both the cytoplasmic and periplasmic sides of the membrane, indicating that the polypeptide binds to the membrane, exposing it to both the outer and inner surfaces of the cytoplasmic membrane. Processing of the precursor was hampered by removal of molybdate from the medium and was restored by its readdition. It was also inhibited by the addition of tungstate in the medium.

Biological Transport↗

PubMed2005

Cold climate phosphorus uptake by submerged aquatic plants in a sewage treatment free water surface wetland.

In November 2002, biomass phosphorus (P) of submerged aquatic plants with associated epiphyton was measured using P-32 tracer addition in a treatment wetland receiving tertiary treated municipal sewage. The wetland is situated 120 km west of Stockholm, Sweden receiving tertiary treated municipal sewage. During the experiment, inflow water had a total P concentration of 0.3 and an iron concentration of 0.7 mg 1(-1) with a residence time of 3-3.5 days. Samples of submerged plants mainly slender waterweed (Elodea nuttallii, L.) and sago pondweed (Potamogeton pectinatus, L.) were taken in two shallow areas (0.21 and 0.51 ha respectively) adjacent to the inlet of one of the wetland subbasins. The sampled area represented 27% of the total 2.6 ha area of the basin. The young phytomass contained 0.02 kg P and the older vegetation parts and epiphyton 0.04 kg P. The sampling took place 90-96 hours after exposure of a pulse of P-32 (18 GBq), i.e. when 75% had passed. Total phytomass was low, only 2 g m(-2) as dry weight. The young phytomass close to the site of injection had higher average beta activity in disintegrations per minute and milligram dry weight (140 DPM mg dw(-1)) than the older parts of the submerged plants (70 DPM mg dw(-1)) indicating an active plant uptake in the former. The latter was interpreted as epiphyton uptake, but since the biomass of old shoots was higher than of young, more P-32 was removed by processes associated with epiphyton as was removed by the young phytomass. In two shallow central zones, the former was equal to 0.006 per thousand of exposed radioactivity in water, while 0.003 per thousand was found in the young phytomass in the same zones of the basin. Close to the inlet a fast P assimilation by the plant biomass was demonstrated. The role of submerged aquatic plants in phosphorus turnover in sewage treatment basins under winter conditions is discussed.

Biomass↗

PubMed1997

Measurement and application of uranium isotopes for human and environmental monitoring.

An improved method is described utilizing extraction chromatography, anion exchange, and alpha spectroscopy for measurement of uranium isotopes in human and environmental surveillance studies. These methods provide a sensitivity of approximately 0.7 mBq per isotope per sample and are generally accurate within the precision of the measurements. The extraction chromatography methods greatly simplify separation of uranium from iron in silicate matrices and provide increased sample throughput and data quality for water, soil, and air filter samples. For bioassay samples, the coprecipitation/anion exchange/alpha spectrometric methods provide rapid throughput and sufficient sensitivity to meet new analytical performance standards in human monitoring studies. In addition, the 234U:238U data can be used as a fingerprint of natural vs. anthropogenic sources of uranium. For 1995 data from our laboratory, a large percentage (79-94% by matrix) of samples appear to be of natural 234U:238U isotopic composition. For all matrices, samples with higher uranium concentration generally have more depleted isotopic composition (smaller 234U:238U). A small percentage of soil (11%), air filter (3%), urine (3%), and water (3%) samples have depleted isotopic signatures at the 95% confidence interval, indicating anthropogenic contributions of uranium to these samples.

Air Pollutants, Radioactive↗

PubMedDate not supplied

[Ceruloplasmin, transferrin and insulin blood levels in those with diabetes mellitus type II and in nondiabetics who participated in the clean-up after the Chernobyl accident].

In those persons who had taken part in the elimination of the effects of the Chernobyl accident (AEEP), an oxidative stress with disturbed functioning of the antioxidant defence extracellular factors ceruloplasmin and transferrin is recordable over a long time range together with direct and indirect manifestations of insulin resistance. Submitted in the paper is an analysis of indices for ceruloplasmin, transferrin, free iron (FI), and insulin in the blood plasma of AEEP in different age groups and in those AEEP suffering from type II diabetes mellitus (DM) as well. The group of comparison was participants in the military operations (MOP) in Afghanistan. In the older age group AEEP (beyond 40 years of age) and in those AEEP presenting with type II DM similar alterations have been shown to be the case, such as decrease in the content of transferrin and augmentation of ceruloplasmin against the background of hyperinsulinemia. The above alterations can be regarded as a risk factor for origination of type II DM in Chernobyl AEEP.

Adult↗

PubMed1994

Magnetically directed poly(lactic acid) 90Y-microspheres: novel agents for targeted intracavitary radiotherapy.

High energy beta-emitting radioisotopes like Yttrium-90 have a radiotoxic range of about one centimeter. For cancer treatment they must be brought near the tumor cells and kept there for as long as they are radioactive. We developed as carriers for the ionic form of 90Y a matrix-type polymeric drug delivery system, poly(lactic acid) (PLA) microspheres. This radiopharmaceutical could be selectively delivered to the target site after incorporating 10% Fe3O4 (magnetite) which made the magnetic microspheres (MMS) responsive to an external magnetic field. Furthermore, MMS are biodegradable and slowly hydrolyze into physiologic lactic acid after the radioactivity is completely decayed. Previously prepared 10-40 microns MMS were radiochemically loaded to high specific activity with 90Y at a pH of 5.7. Stability studies showed that approximately 95% of added 90Y is retained within the PLA matrix after 28 days (> 10 half-lives) at 37 degrees C in serum, and electron microscopy showed that the microspheres retained their characteristic morphologic appearance for the same time period. Cytotoxicity studies with SK-N-SH neuroblastoma cells growing in monolayer showed that the radiocytotoxicity of the microspheres could be directed magnetically to either kill or spare specific cell populations, thus making them of great interest for targeted intracavitary tumor therapy. We are currently optimizing this system for use in the treatment of neoplastic meningitis.

Animals↗

PubMed1990

In vivo stability of ferric hydroxide macroaggregates (FHMA). Is it a suitable carrier for radionuclides used in synovectomy?

Ferric hydroxide macroaggregates (FHMA) have been widely used as a carrier for several radionuclides used in radiation synovectomy. Different rates of extra-articular leakage of radioactivity have been observed with 90Y and 165Dy. In order to understand the mechanism(s) involved in the extra-articular leakage of radioactivity, the in vivo stability of FHMA carrier was studied. Following an injection of [59Fe]Fe-FHMA into the knees of normal rabbits, the cumulative leakage of [59Fe]Fe-FHMA was 2.9% at 5 days and 12.3% at 14 days. More than 60% of this activity was in the blood. But when FHMA was double labeled with 59Fe and 166Ho, the 59Fe leakage significantly increased to 18.5% at 5 days and 27% by 14 days. The instability of FHMA is accelerated when it is complexed with 166Ho and may be due to the "mass effect" of 166Ho or due to radiolysis induced by high energy beta particles from 166Ho. These results suggest that FHMA is a suitable carrier only for the short lived radionuclides used in synovectomy.

Animals↗

PubMed1997

4-hydroxybenzoyl coenzyme A reductase (dehydroxylating) is required for anaerobic degradation of 4-hydroxybenzoate by Rhodopseudomonas palustris and shares features with molybdenum-containing hydroxylases.

The anaerobic degradation of 4-hydroxybenzoate is initiated by the formation of 4-hydroxybenzoyl coenzyme A, with the next step proposed to be a dehydroxylation to benzoyl coenzyme A, the starting compound for a central pathway of aromatic compound ring reduction and cleavage. Three open reading frames, divergently transcribed from the 4-hydroxybenzoate coenzyme A ligase gene, hbaA, were identified and sequenced from the phototrophic bacterium Rhodopseudomonas palustris. These genes, named hbaBCD, specify polypeptides of 17.5, 82.6, and 34.5 kDa, respectively. The deduced amino acid sequences show considerable similarities to a group of hydroxylating enzymes involved in CO, xanthine, and nicotine metabolism that have conserved binding sites for [2Fe-2S] clusters and a molybdenum cofactor. Cassette disruption of the hbaB gene yielded a mutant that was unable to grow anaerobically on 4-hydroxybenzoate but grew normally on benzoate. The hbaB mutant cells did not accumulate [14C]benzoyl coenzyme A during short-term uptake of [14C]4-hydroxybenzoate, but benzoyl coenzyme A was the major radioactive metabolite formed by the wild type. In addition, crude extracts of the mutant failed to convert 4-hydroxybenzoyl coenzyme A to benzoyl coenzyme A. This evidence indicates that the hbaBCD genes encode the subunits of a 4-hydroxybenzoyl coenzyme A reductase (dehydroxylating). The sizes of the specified polypeptides are similar to those reported for 4-hydroxybenzoyl coenzyme A reductase isolated from the denitrifying bacterium Thauera aromatica. The amino acid consensus sequence for a molybdenum cofactor binding site is in HbaC. This cofactor appears to be an essential component because anaerobic growth of R. palustris on 4-hydroxybenzoate, but not on benzoate, was retarded unless 0.1 microM molybdate was added to the medium. Neither tungstate nor vanadate replaced molybdate, and tungstate competitively inhibited growth stimulation by molybdate.

Amino Acid Sequence↗

PubMed2000

Intravascular circulation and distribution of human 51Cr-DBBF stroma-free hemoglobin, 51Cr-plasma, 51Cr-saline, 59FE-plasma, and 125I-albumin in the mouse.

Male B6C3HF1 mice were infused with human 51Cr-labeled DBBF (bis 3,5-dibromosalicyl fumarate) crosslinked stroma-free hemoglobin (SFH). In the first hour following SFH infusion, 11.2% of the infused radioactivity was found in the skin, 11.4% in muscle, 9.1% in the skeleton, and 5% in the liver. Twenty-four hours after infusion, 15.4% of the radioactivity was found in the skin, 10.3%, in the muscle, 16.6% in the skeleton, and 6.7% in the liver. The circulation and distribution of 51Cr-labeled DBBF-SFH were compared with levels of 51Cr labeled plasma, 51Cr in saline, 59Fe labeled plasma, and 125I albumin. The radioactivity in the blood was similar for 51Cr-DBBF-SFH, 51Cr-plasma, and 59Fe-plasma. During the 24-hour post-infusion period, extravascular distribution of the 51Cr-saline, 51Cr-plasma, and 125I albumin within the organs was similar to that of 51Cr-DBBF-SFH, with the highest levels being in skin, muscle, skeleton and liver, and no increase in the levels in the lung or spleen. The distribution of 59Fe compared to that of 51Cr-DBBF, 51Cr-plasma, 51Cr-saline, and 125I albumin can be explained by the fact that 59Fe is utilized in the production of new red blood cells.

Albumins↗

PubMed1976

Quantitation of Friend spleen focus-forming virus by a nine-day 59Fe assay.

A previously described 3-day 59Fe assay for quantitation of Friend spleen focus-forming virus has been modified to produce a 200-fold more sensitive 9-day 59Fe assay. A characterization of this assay is reported here. Male BALB/c mice received intravenous injections of appropriately diluted Friend polycythemia virus (FVP); control mice received virus diluent. All mice were allowed food and water ad libitum for 6 days, and on day 6 after virus injection were fasted by removal of food but not water. On day 3 of the fast (the 9th day after virus injection) each mouse received an intraperitoneal injection of 1 muCi of 59Fe. Six hours later the mice were sacrificed and the splenic radioactivity was determined. The percent splenic incorporation of 59Fe was directly related to the logarithm of spleen focus-forming units (SFFU) of FVP injected in a range of approximately 25 to 1,000 SFFU. Using a standard FVP preparation in a dose range of 25 to 1,000 SFFU, it was possible to determine the SFFU titers of unknown samples by extrapolation of the percent splenic 59Fe incorporation to the logarithm of SFFU. SFFU titers obtained by the 9-day 59Fe assay were similar to those obtained by the enumerative-response assay. Advantages of the 9-day 59Fe assay over the enumerative-response assay include a 50-fold greater virus dose range, an easier and a more objective counting procedure, and a reduced coefficient of variation.

Animals↗

PubMedDate not supplied

N-(iodoacetyl)-p-phenylenediamine-EDTA: a reagent for high-efficiency incorporation of an EDTA-metal complex at a rationally selected site within a protein.

We have developed a highly efficient procedure to incorporate an EDTA:metal complex at a rationally selected site within a full-length protein. Our procedure has two steps: In step one, we use site-directed mutagenesis to introduce a unique solvent-accessible cysteine residue at the site of interest. In step two, we derivatized the resulting protein with N-(iodoacetyl)-p-phenylenediamine-EDTA:metal, a novel haloacetyl derivative of EDTA:metal. We have used this procedure to incorporate each of three EDTA:metal complexes at amino acid 2 of the helix-turn-helix motif of the sequence-specific DNA binding protein Cro: a radioactive and nucleolytic EDTA:metal complex (EDTA:55Fe), a radioactive EDTA:metal complex (EDTA:63Ni), and a fluorescent and heavy-atom EDTA:metal complex (EDTA:Eu). Incorporation of EDTA:metal was highly efficient (> 80% for EDTA:55Fe and EDTA:63Ni; 60% for EDTA:Eu) and highly site-specific (> 99%). We have analyzed DNA affinity cleaving by the Cro derivative having EDTA:55Fe at amino acid 2 of the helix-turn-helix motif. The Cro derivative cleaves DNA at base pairs -4 to 6 of the DNA half site in the protein-DNA complex, indicating that amino acid 2 of the helix-turn-helix motif of Cro is close to base pairs -4 to 6 of the DNA half site in the Cro-DNA complex in solution.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteriophage lambda↗