Alkaline Denaturation Research Articles

Spectroscopic and dosimetric comparison of tooth enamel separation methods for EPR retrospective dosimetry

Precise estimation of individual radiation dose utilizing biomaterials (fingernail, bone, and tooth) is very challenging due to their complex sample processing. Despite, tooth enamel, the most mineralized tissue of tooth is used for this purpose due to its high radiation sensitivity and ability to produce radiation induced long lived CO2− radicals. However, human teeth are not always available, and invasive nature of sample collection adds to the complexity making dose estimation difficult. In such cases, animal teeth (goat, cow, and moose) can be used as a substitute for human teeth due to comparable enamel sensitivity. Moreover, separation of enamel from dentine is a crucial step towards accurate dose estimation from irradiated teeth. In this work, Indian goat teeth were used as it was readily available to us and the comparison of goat enamel sensitivity to radiation was found to be within ∼7.4 % that of human. The enamel samples were separated following two chemical methods; (1) density separation using sodium polytungstate, (2) alkaline denaturation using NaOH and the quality was compared based on their purity and radiation sensitivity. Combined results of spectroscopic characterization using X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Raman analysis authenticated the crystallinity and purity of the separated enamel samples. The radiation sensitivity of separated enamel samples was compared by electron paramagnetic resonance (EPR) analysis as a part of dosimetric characterization. The suitability of both the samples for retrospective dosimetry and epidemiological studies was checked by validating the dose estimated from separated enamel samples with standard alanine/EPR dosimeter.

Characterization of structural and functional properties of soybean 11S globulin during renaturation after denaturation induced by changes in pH.

This study explored the denaturation of 11S globulin, a protein known for its diverse functional properties in soy protein applications, at pH 3.0 and pH 10.0, followed by a gradual return to pH 7.0 to facilitate renaturation. It investigated the structural and functional changes during renaturation induced by a change in pH, revealing the stabilization mechanism of 11S globulin. The findings revealed that during pH adjustment to neutral, the denatured soybean 11S globulin - resulting from alkaline (pH 10.0) or acidic (pH 3.0) treatments - experienced a refolding of its extended tertiary structure to varying extents. The particle size and the proportions of α-helix and β-sheet in the secondary structure aligned progressively with those of the natural-state protein. However, for the alkali-denatured 11S, the β-sheet content decreased upon adjustment to neutral, whereas an increase was observed for the acid-denatured 11S. In terms of functional properties, after alkaline denaturation, the foaming capacity (FC) and emulsifying activity index (EAI) of 11S increased by 1.4 and 1.2 times, respectively, in comparison with its native state. The solubility, foamability, and emulsifiability of the alkali-denatured 11S gradually diminished during renaturation but remained superior to those of the native state. Conversely, these properties showed an initial decline, followed by an increase during renaturation triggered by pH neutralization. This research contributes to the enhancement of protein functionality, offering a theoretical foundation for the development of functional soy protein products and expanding their potential applications. © 2024 Society of Chemical Industry.

Allelic Diversification of the Wx and ALK Loci in Indica Restorer Lines and Their Utilisation in Hybrid Rice Breeding in China over the Last 50 Years.

Hybrid rice technology has been used for more than 50 years, and eating and cooking quality (ECQ) has been a major focus throughout this period. Waxy (Wx) and alkaline denaturation (ALK) genes have received attention owing to their pivotal roles in determining rice characteristics. However, despite significant effort, the ECQ of restorer lines (RLs) has changed very little. By contrast, obvious changes have been seen in inbred rice varieties (IRVs), and the ECQ of IRVs is influenced by Wx, which reduces the proportion of Wxa and increases the proportion of Wxb, leading to a decrease in amylose content (AC) and an increase in ECQ. Meanwhile, ALK is not selected in the same way. We investigated Wx alleles and AC values of sterile lines of female parents with the main mating combinations in widely used areas. The results show that almost all sterile lines were Wxa-type with a high AC, which may explain the low ECQ of hybrid rice. Analysis of hybrid rice varieties and RLs in the last 5 years revealed serious homogenisation among hybrid rice varieties.

Towards the Selection of Single‐Stranded DNA Molecular Recognition Element Against Cyanotoxin L‐BMAA

Global warming, anthropogenic pressure and eutrophication contribute to the formation and persistence of cyanobacterial blooms in aquatic environments. Cyanotoxins produced during these blooms represent a threat to ecosystems, commercial industries and human health. B‐N‐methylamino‐L‐alanine (L‐BMAA) is a neurotoxic amino acid that has been linked to neurodegenerative diseases such as Amyotrophic Lateral Sclerosis/Parkinsonism Dementia Complex (ALS/PDC), Alzheimer’s disease (AD) and Amyotrophic Lateral Sclerosis (ALS). Research has shown that L‐BMAA can act as a glutamate receptor antagonist and can incorporate into proteins occasioning protein misfolding that leads to detrimental processes in brain tissues. Currently, the detection of L‐BMAA is costly, time‐consuming and labor‐intensive. Many research groups around the world are working towards the development of bioanalytical methods to improve the detection of these toxins, including the development of molecular biorecognition elements (MREs) that can provide analyte specificity in biosensing applications. Among MREs, aptamers are well‐known to possess an extraordinary target recognition due to the formation of unique three‐dimensional structures capable of binding specifically to their respective targets.We aim to perform an in vitro selection of a single‐stranded DNA (ssDNA) aptamer that can act as an MRE against L‐BMAA, using the systematic evolution of ligands by exponential enrichment (SELEX) technique. We have worked on the optimization of incubation conditions, PCR amplification parameters and the generation of ssDNA using two different ssDNA libraries, with randomized regions of varying lengths. To facilitate the separation of bound and unbound ssDNA after incubation with the target, we modified L‐BMAA with a biotinylated linker to immobilize it in streptavidin‐coated magnetic beads. For each library, we have identified the appropriate annealing temperature, primer concentrations and number of cycles to favor the amplification of the main product while minimizing by‐product formation. The most challenging step of the SELEX procedure has been the generation and purification of ssDNA in sufficient amounts to continue to the next round of selection. To achieve this, we have tried four main methods: exonuclease digestion, size separation derived from uneven primers, asymmetric PCR and alkaline denaturation using sodium hydroxide. Hitherto, we have completed the first round of selection with both libraries, by performing large‐scale PCR reactions and alkaline denaturation followed by ethanol precipitation to generate the ssDNA. We are working in the first round of negative selection to discard those sequences with affinity to the immobilization linker and enrich only those that bind exclusively to L‐BMAA. Given that our target is a small molecule, our goal is to conduct a stringent SELEX process to obtain a highly specific MRE that can be incorporated into an environmental sensing device.

Rapid DNA interstrand cross-linking of Pt(IV) compound

Pt(IV) anticancer compounds have been developed for several decades to overcome the drawbacks of their Pt(II) congeners, and the reduction of Pt(IV) to Pt(II) has been commonly regarded as a necessary step in the activation of Pt(IV) compounds prior to targeting DNA. However, blockage of glutathione (GSH) biosynthesis resulted in a slight effect on the cytotoxicity of oxoplatin in yeast Saccharomyces cerevisiae strains, urging us to reconsider the mechanism of actions for the “inert” Pt(IV) complexes. Using X-ray absorption near-edge spectroscopy (XANES), our data demonstrated that Pt(IV) complex oxoplatin could bind to DNA in a tetravalent state. Both alkaline denaturing agarose electrophoresis and thermal denaturation-renaturation assay revealed that oxoplatin could rapidly produce stable interstrand crosslinks (ICLs), which can further translate into a fast cell-killing process in cancer cells. Using quantitative real-time PCR and immunofluorescence analysis, we also proved that Pt(IV) complex oxoplatin could induce a quick intracellular response of the FA/BRCA pathway in cancer cells that involves the DNA interstrand crosslinking repair system, and this quick response to ICLs was independent with the intracellular GSH levels. Cell cycle analysis showed that short incubation with oxoplatin can induce a strong S phase arrest in HeLa cells, indicating that the rapid interstrand crosslinks produced by oxoplatin might stall the replication fork, result in the double-strand breaks, and eventually induce cell death. Our results implied that, besides the reduction mechanism to release the Pt(II) congeners, direct and rapid interstrand cross-linking with DNA by Pt(IV) compounds might be a unique mechanism for Pt(IV) compounds, which may provide new insight for the development of next-generation platinum-based drugs.

High-efficiency enrichment enables identification of aptamers to circulating Plasmodium falciparum-infected erythrocytes

Plasmodium falciparum is the causative agent of the deadliest human malaria. New molecules are needed that can specifically bind to erythrocytes that are infected with P. falciparum for diagnostic purposes, to disrupt host-parasite interactions, or to deliver chemotherapeutics. Aptamer technology has the potential to revolutionize biological diagnostics and therapeutics; however, broad adoption is hindered by the high failure rate of the systematic evolution of ligands by exponential enrichment (SELEX). Here we performed parallel SELEX experiments to compare the impact of two different methods for single-strand recovery on the efficiency of aptamer enrichment. Our experimental results and analysis of SELEX publications spanning 13 years implicate the alkaline denaturation step as a significant cause for inefficient aptamer selection. Thus, we applied an exonuclease single-strand recovery step in our SELEX to direct aptamers to the surface of erythrocytes infected with P. falciparum. The selected aptamers bind with high affinity (low nanomolar Kd values) and selectivity to exposed surface proteins of both laboratory parasite strains as well isolates from patients in Asia and Africa with clinical malaria. The results obtained in this study potentially open new approaches to malaria diagnosis and surveillance.

Strand-specific detection of overlapping transcripts via purification involving denaturation of biotinylated cDNA.

Reverse transcription-PCR (RT-PCR) is the most widely employed technique for gene expression analysis owing to its high sensitivity, easy reproducibility and fast output. It has been conceived that priming RT reactions with gene-specific primers generates cDNA only from the specific RNA. However, several reports have revealed that cDNA is synthesized even without addition of exogenous primers in RT reactions. Owing to such self-priming activity, the signals from specific strands cannot be accurately detected and can confound the expression analysis, especially in context of overlapping bidirectional transcripts. Here, we demonstrate that purification of biotin-tagged cDNA in conjunction with alkaline denaturation can obviate the problem of background priming and enable accurate strand-specific detection of overlapping transcripts.

Detection of Alkali-Labile Sites on Satellite DNA by DNA Breakage Coupled with Fluorescence in Situ Hybridization (DNA-FISH) Monitor DNA Damage in Cervical Epithelial Cells

Satellite DNA is the main component of functional centromeres and forms the main structural constituent of heterochromatin. The presence of alkali-labile sites (ALSs) is a feature inherent to chromatin structure. Here we aimed to characterize ALSs in different satellite DNA loci in cervical epithelial cells using DNA breakage detection coupled with fluorescence in situ hybridization (DBD–FISH). Cervical epithelial cells embedded in an agarose matrix were deproteinized and exposed to alkaline denaturation, which generated single-stranded DNA (ssDNA) starting from the ends of spontaneous basal DNA breaks and ALSs. The amount of ssDNA produced within a specific sequence area could be detected by DBD–FISH using specific probes. The DBD–FISH signals, which were corrected for respective FISH signals during metaphase, were remarkably stronger in the 5 bp classical satellite DNA domains analyzed (D1Z1, D9Z3, and D16Z3) compared with alphoid satellite regions (D3Z1, D8Z2, and DXZ1). D1Z1 locus of chromome-1 being the most affected by alkali denaturation, and contrary, D3Z1 locus of chromosome–3 was the least sensitive to alkali treatment. These findings suggest a high density of constitutive ALSs—probably abasic sites—within the 5 bp satellite DNA sequences in cervical epithelial cells. The presence and relative abundance of ALSs might help explain the high frequency of spontaneous breakage and rearrangements in the pericentromeric heterochromatin of chromosomes 1, 9, and 16 when this chromatin region is undercondensed spontaneously or via induction, such as following viral infections. ALSs in these sequences could be useful tools to monitor DNA damage in cases of cervical carcinogenesis. ALSs on these sequences could be useful tools to monitor DNA damage in cases of cervical carcinogenesis.

Effects of ionic and reductive atmosphere on the conformational rearrangement in hen egg white lysozyme prior to amyloid formation

In this study, the combined effects of pH and salt concentration on the aggregation and amyloid formation of a charge-bearing protein (hen egg white lysozyme, HEWL) were investigated, as well as the inhibition of amyloid formation by using dithiothreitol (DTT) as a denaturing agent. Amyloid formation was found to depend on the ion strength and pH of the sample solution. Rather than the total charge, the partial charge of the amyloid related residues contributes to amyloid formation at pH < isoelectric point (pI). On the other hand, at pH> pI HEWL only undergoes alkaline denaturation regardless of the ionic strength. The effect of adding different amounts of DTT at different times on amyloid formation was also investigated. These results suggested that the positions of charges on a protein and the protein secondary structure are critical for protein aggregation and amyloid formation.

Systematic FTIR Spectroscopy Study of the Secondary Structure Changes in Human Serum Albumin under Various Denaturation Conditions.

Human serum albumin (HSA) is the most abundant protein in blood plasma. HSA is involved in the transport of hormones, fatty acids, and some other compounds, maintenance of blood pH, osmotic pressure, and many other functions. Although this protein is well studied, data about its conformational changes upon different denaturation factors are fragmentary and sometimes contradictory. This is especially true for FTIR spectroscopy data interpretation. Here, the effect of various denaturing agents on the structural state of HSA by using FTIR spectroscopy in the aqueous solutions was systematically studied. Our data suggest that the second derivative deconvolution method provides the most consistent interpretation of the obtained IR spectra. The secondary structure changes of HSA were studied depending on the concentration of the denaturing agent during acid, alkaline, and thermal denaturation. In general, the denaturation of HSA in different conditions is accompanied by a decrease in α-helical conformation and an increase in random coil conformation and the intermolecular β-strands. Meantime, some variation in the conformational changes depending on the type of the denaturation agent were also observed. The increase of β-structural conformation suggests that HSA may form amyloid-like aggregates upon the denaturation.

Coexistence of hemoglobin Handsworth and alpha 3.7 kb deletion in Caucasian woman in Poland

AbstractBackgroundThis report presents a case of an adult Polish women of Caucasian origin who was heterozygous for the nondeletional mutation: Hb Handsworth (HBA2 or HBA1: c.55G &gt; C, p.Gly19Arg) and deletional (-α3.7) α-thalassemia mutation.MethodsThe HbA2 and HbF levels were measured by microcolumn chromatography and alkaline denaturation procedure, respectively, while electrophoresis was used to detect pathological hemoglobin fraction. The β- and α-globin genotypes were determined by DNA sequencing, gap-polymerase chain reaction, α gene triplication and MLPA.ResultsThe HbA2 and HbF levels were normal, but hemoglobin electrophoresis on agarose gel alkaline pH showed a strong band migration in a position of hemoglobin S and faint bands in the neighborhood of band A on acid electrophoresis. Molecular analysis of the alpha globin cluster detected a point mutation at codon 19 in HBA2 (c.55G &gt; C, p.Gl- y19Arg) and deletion -α3.7.ConclusionsOur compound heterozygosity does not produce severe clinical or hematological symptoms but it is important to say that in our part of Europe such cases do appear. Molecular analysis of the alpha globin cluster is required for correct diagnosis in patients with normal HbA2 levels. Compound heterozygosity was unmasked by molecular diagnosis only.

Bifunctional Phenol Quinone Methide Precursors: Synthesis and Biological Activity

New bifunctional quinone methide (QM) precursors, bisphenols 2a–2e, and monofunctional QM precursor 7 were synthesized. Upon treatment with fluoride, desilylation triggers formation of reactive intermediates, QMs, which was demonstrated by trapping QM with azide or methanol. The ability of QMs to alkylate and cross-link DNA was assayed by investigation of the effects of QMs to DNA denaturing, but without conclusive evidence. Furthermore, treatment of a plasmid DNA with compounds 2a–2e and KF, followed by the analysis by alkaline denaturing gel electrophoresis, did not provide evidence for the DNA cross-linking. MTT test performed on two human cancer cell lines (MCF7 breast adenocarcinoma and SUM159 pleomorphic breast carcinoma), with and without fluoride, indicated that 2a–2e or the corresponding QMs did not exhibit cytotoxic activity, in line with the lack of ability to cross-link DNA. The lack of reactivity with DNA and biological activity were explained by sequential formation of QMs where bifunctional cytotoxic reagent is probably never produced. Instead, the sequential generation of monofunctional QM followed by a faster hydrolysis leads to the destruction of biologically active reagent. The findings described here are particularly important for the rational design of new generation of QM precursor molecules that will attain desirable DNA reactivity and cytotoxicity.

Glutaraldehyde crosslinked and alkaline denaturation induced self association of haemoglobin to design nanocarriers for In vitro release of insulin in simulated gastrointestinal fluids (SGFs)

Adopting a novel synthetic route the haemoglobin nanoparticles were prepared by its simultaneous microemulsion mediated crosslinking with glutaraldehyde and alkaline induced denaturation. The as prepared nanoparticles were characterized by techniques like Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), Scanning electron microcopy (SEM), Zeta potential and Dynamic Light Scattering measurements. The particle size analysis revealed that size of the nanoparticles lays in the range 60–150 nm with surface charge of −27.1 mV. The TEM images suggested for aggregated structures which confirm denaturation of haemoglobin macromolecules under alkaline conditions. The nanoparticles were assessed for water intake capacity and the effect of various factors like chemical composition of nanoparticles, pH and temperature of the swelling bath, and simulated biological fluids on water sorption capacity was investigated. The insulin was loaded on to the prepared nanoparticles and investigated for swelling controlled release of insulin in simulated gastrointestinal fluid (SGIFs). The influence of chemical composition of nanoparticles, pH and temperature of the release media, and simulated physiological fluids was studied on the released amount of insulin and an optimized formulation was achieved. The prepared haemoglobin nanoparticles were also investigated for their in-vitro cytotoxicity.

Alkaline Denaturing Southern Blot Analysis to Monitor Double-Strand Break Processing.

Generation of 3' single-stranded DNA (ssDNA) tails at the ends of a double-strand break (DSB) is essential to repair the break through accurate homology-mediated repair pathways. Several methods have been developed to measure ssDNA accumulation at a DSB in the budding yeast Saccharomyces cerevisiae. Here, we describe one of these assays, which is based on the inability of restriction enzymes to cleave ssDNA. Digestion of genomic DNA prepared at different time points after DSB generation leads to the formation of ssDNA fragments whose length increases as the 5' strand degradation proceeds beyond restriction sites. After the separation by electrophoresis on alkaline denaturing agarose gel, these ssDNA fragments can be visualized by hybridization with an RNA probe that anneals with the 3'-undegraded DSB strand. This assay allows a direct and comprehensive visualization of DSB end processing.

Significantly elevated foetal haemoglobin levels in individuals with glucose 6-phosphate dehydrogenase disease and/or sickle cell trait: a cross-sectional study in Cape Coast, Ghana

BackgroundPreviously published data have demonstrated that sickle red blood cells produce twice as much reactive oxygen species (ROS) suggesting that co-inheritance of sickle cell disease (SCD) and glucose 6-phosphate dehydrogenase (G6PD) enzymopathy could lead to more severe anaemia during sickling crises. Elevated foetal haemoglobin (Hb F) levels have been shown to have positive modulatory effects on sickling crises and disease outcomes. This study sought to assess how inheritance of G6PD enzymopathy affects the level of Hb F and haemoglobin concentration in adults in steady state.MethodsThis cross-sectional study selected 100 out-patients (41 males and 59 females) visiting the University of Cape Coast hospital, between January, 2016 and May, 2016. Cellulose acetate electrophoresis (pH 8.2–8.6), methaemoglobin reductase test, modified Betke alkaline denaturation methods were used to investigate haemoglobin variants, qualitative G6PD status, and %Hb F levels in venous blood samples drawn from these participants. Data was analysed with GraphPad Prism 6 and SPSS and significance set at p < 0.05.ResultsForty one percent of the participants demonstrated qualitative G6PD enzymopathy whereas only 10% demonstrated Hb AS type (Sickle cell trait, SCT). 5% of the participants co-inherited SCT and G6PD enzymopathy. %Hb F levels in G6PD deficient males was significantly higher than in G6PD deficient females [(p = 0.0003, 2.696% (males) vs 1.975% (females)], although the %Hb F levels was comparable in non-G6PD deficient individuals. %Hb F levels were significantly elevated in males with SCT only (p < 0.05), or G6PD enzymopathy only (p < 0.0001), or SCT + G6PD enzymopathy (p < 0.0001) compared to males with none of these pathologies even though their respective haemoglobin levels were comparable. Male participants with G6PD enzymopathy + SCT co-inheritance had significantly elevated %Hb F when compared to their counterparts with only G6PD enzymopathy (p < 0.001). Male gender [(p = 0.001, OR: 6.912 (2.277–20.984)] partial defective G6PD enzyme [(p = 0.00, OR: 7.567E8 (8.443E7–6.782E9)] SCT [(p = 0.026, OR: 4.625 (1.196–17.881)] were factors associated with raised %Hb F levels ≥2.5.ConclusionThe inheritance of G6PD defect and/or SCT significantly elevate %Hb F levels in the steady state even though haemoglobin levels are not affected.

Assessment of Sperm Deoxyribose Nucleic Acid Fragmentation Using Sperm Chromatin Dispersion Assay.

The integrity of sperm deoxyribose nucleic acid (DNA) is one of the determinants that ensure normal fertilization, implantation, pregnancy, and the generation of a healthy progeny. Assessment of sperm DNA fragmentation has gained importance as a tool to provide significant information regarding sperm quality, and it can independently predict sperm fertilizing potential. The sperm chromatin dispersion (SCD) assay is one of the available techniques to detect sperm DNA damage with results comparable to the gold standard – Sperm Chromatin Structure Assay. We present here a detailed methodology of an alkaline modification of SCD that can be carried out with minimal laboratory equipment. The SCD assay is a modified halo assay that utilizes chemical methods to demonstrate sperm DNA fragmentation. It involves the embedding of sperms in an agarose medium followed by exposure to alkaline denaturation and deproteinization. The results are interpreted under a light microscope. A visual scoring system is utilized to differentiate the sperms with possible DNA fragmentation from those without fragmented DNA and to determine the sperm DNA fragmentation index (SDFI) % for each semen sample. The SDFI % is directly proportional to the quality of sperm. The SCD assay is a simple, cost-effective, and reliable technique that can detect sperm DNA fragmentation, thus providing information regarding sperm functional quality and reproductive capacity. It is of significance in clinical and research areas of andrology and reproductive medicine, toxicology, and pharmacotherapeutics.

Emerging spread of β-thalassemia trait in Nigeria

BackgroundChronic anaemia mainly thalassemia and sickle cell anaemia are inherited disorders of haemoglobin. Presently about 7% of the world's populations are carriers of a potentially pathological haemoglobin gene. Sickle cell disease is a common haemoglobinopathy in Nigeria but recently cases of β-thalassemia traits are becoming prominent. This study aimed at screening for β-thalassemia in adults and children with chronic anaemia in Nigeria by assessing the patients’ level of haemoglobin F, haemoglobin A2 and red cell indices. Materials and methodsHaemoglobin F and HbA2 were determined in the chronic anaemia patients by Alkaline Denaturation Method and Beta-Thal HbA2 Quick Column Procedure respectively. Haemoglobin genotype was determined by Haemoglobin Electrophoresis at alkaline medium while Complete Blood count was estimated using Sysmex KX-2IN Autoanalyser. ResultsThe mean HbF, HbA2, HCT, MCV, MCH and MCHC of the children and adults are 2.56±0.46 and 2.45±0.87 (%); 2.05±0.25 and 1.89±0.60 (%); 0.21±0.31 and 0.21±0.36 (L/L); 81.58±12.59 and 78.69±14.11 (fL); 22.74±5.39 and 23.07±7.36 (pg); 27.52±3.84 and 31.23±14.32 (g/l) respectively. Four percent (2 subjects) of each adult and children population had increased HbF level (>1.5%) and HbA2 levels (>2.8%) and these subjects are composed of 2 children with haemoglobin genotype AA and two adult with haemoglobin genotypes SS. ConclusionsThe outcome of this study reiterates the emergence of β-thalassemia traits and iron deficiency anaemia in different parts of Nigeria irrespective of their haemoglobin genotype status. This requires adequate specialized intervention for their diagnosis and treatment. There is therefore the need for subsequent molecular analysis to determine the β-thalassemia genes present in the studied community.

Coinheritance of B-Thalassemia and Sickle Cell Anaemia in Southwestern Nigeria.

Genes for haemoglobin S are found in high frequencies in Nigeria. However, there is little information on beta thalassemia in sickle cell anaemia in this population. The clinical presentation of HbS- β thalassemia is enormously variable, ranging from an asymptomatic state to a severe disorder similar to homozygous sickle cell disease. Haemoglobin A2 and HbF were determined in sickle cell anaemia patients attending LAUTECH Teaching Hospital, Osogbo, by elution after electrophoresis and alkaline denaturation methods respectively. Haematological parameters were estimated using Sysmex KX-21N and percentage target cells using Leishman's staining technique. Exactly 6% f the SCA patients were found to have elevated HbA2 (>3.3%) and HbF (>1.3%). These patients also had normal erythrocyte indices, increased platelet count, a significantly higher HCT and an increased % target cell. These findings confirm that the frequency of beta thalassaemia in sickle cell patients in Nigeria is higher than previously thought. It is therefore important to consider the possibility of this variant in patients with sickle cell anaemia since their course may differ from that of patients with homozygous sickle cell anaemia.

Genetic variants associated with fetal hemoglobin levels show the diverse ethnic origin in Colombian patients with sickle cell anemia.

Fetal hemoglobin is an important factor in modulating the severity of sickle cell anemia. Its level in peripheral blood underlies strong genetic determination. Associated loci with increased levels of fetal hemoglobin display population-specific allele frequencies. We investigated the presence and effect of known common genetic variants promoting fetal hemoglobin persistence (rs11886868, rs9399137, rs4895441, and rs7482144) in 60 Colombian patients with sickle cell anemia. Four single nucleotide polymorphisms (SNP) were genotyped by restriction fragment length polymorphisms (RFLP) and the use of the TaqMan procedure. Fetal hemoglobin (HbF) from these patients was quantified using the oxyhemoglobin alkaline denaturation technique. Genotype frequencies were compared with frequencies reported in global reference populations. We detected genetic variants in the four SNPs, reported to be associated with higher HbF levels for all four SNPs in the Colombian patients. Genetic association between SNPs and HbF levels did not reach statistical significance. The frequency of these variants reflected the specific ethnic make-up of our patient population: A high prevalence of rs7482144-'A' reflects the West-African origin of the sickle cell mutation, while high frequencies of rs4895441-'G' and rs11886868-'C' point to a significant influence of an Amerindian ethnic background in the Colombian sickle cell disease population. These results showed that in the sickle cell disease population in Colombia there is not a unique genetic background, but two (African and Amerindian). This unique genetic situation will provide opportunities for a further study of these loci, such as fine-mapping and molecular-biological investigation. Colombian patients are expected to yield a distinctive insight into the effect of modifier loci in sickle cell disease.

Mechanisms of cytotoxicity for bifunctional epoxide alkylating agents

The discovery that bifunctional alkylating agents have antitumor activity led to the development of cancer chemotherapy over 50 years ago, yet these compounds also lead to an increased risk of secondary cancers. Bifunctional alkylating agents form a variety of DNA adducts, including monoadducts, intrastrand cross‐links, and interstrand cross‐links. Interstrand cross‐links are believed to be the most lethal, impeding both replication and expression of the genetic material. We are characterizing the mechanisms by which diepoxybutane (DEB) and epichlorohydrin (ECH) exert their cytotoxic effects in cultured cells. Our first goal is to determine the relationship between interstrand cross‐linking and cytotoxicity in human acute myeloid leukemia (HL60) cells. HL60 cells are treated with varying concentrations of the compound of interest and assayed to determine the fraction of cells that remain viable, allowing determination of LD50 values. Cross‐linking ability is assessed using an ethidium bromide assay to determine the amount of duplex DNA following alkaline denaturation. Only cross‐linked DNA reanneals rapidly and interacts with the dye, which is highly fluorescent when bound to duplex DNA. Preliminary results suggest a correlation between cross‐linking and LD50 values for these compounds, with DEB a more efficient cross‐linker than ECH.Our second goal is to identify the structures of ECH‐cross‐linked lesions via ESI‐TOF‐MS, which may provide information about the mechanism of this agent. This research was supported by an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under grant number P20GM103423.