Metal–DNA interactions

Design and demonstration of a temperature-resistant aptamer structure for highly sensitive mercury ion detection with BioFETs

In this study, we developed a temperature-resistant aptamer coupled with extended gate electric double-layer Field-Effect Transistors (FETs) for highly sensitive mercury ion detection. The design of the temperature-resistant aptamer is based on the thermal and structural properties of the hairpin structure. Two aptamer sequences were designed with different melting temperatures (Tm) and compared for their sensitivity. The hairpin structure of the aptamer with a high melting temperature ensures the stable structure prior to the addition of the mercury ions, which allows the formation of thymine-mercury-thymine (T -Hg2+-T) complex in low concentrations of mercury ions. High sensitivity and low detection limit are achieved at elevated temperatures with the aptamer having a high melting temperature. The elevated temperature facilitates the reaction rate, resulting in high sensitivity and a low detection limit. The aptamer with a high melting temperature hairpin structure has shown a remarkable improvement in the limit of detection with a 4 orders of magnitude increase compared to the one with a low melting temperature. The sensor with the high melting temperature aptamer shows an extremely low detection limit of 4.68 × 10-12 M, surpassing previously reported results. The aptamer with a low melting temperature requires mercury ions to stabilize the hairpin structure by forming a T-Hg2+-T complex. The results show that if the melting temperature is lower than the ambient temperature, it is very difficult to detect low concentrations of mercury ions at the ambient temperature. The selectivity of this sequence was also tested against multiple heavy metals, including arsenic (As), lead (Pb), chromium (Cr), and cadmium (Cd) ions. This study has shown how the structural and thermal properties of the aptamer, and the ambient temperature affect the sensitivity. They are strongly correlated to the performance of the sensors and need to be considered in the design of the sequence.

Understanding Cu+2 binding with DNA: A molecular dynamics study comparing Cu2+ and Mg2+ binding to the Dickerson DNA

Cu2+ ions led DNA damage by reactive oxygen species (ROS) is widely known biological phenomena. The ionic radii of Cu2+ and Mg2+ being similar, the binding of Cu2+ ions to DNA is expected to be similar to that of the Mg2+ ions. However, little is known how Cu2+ ions bind in different parts (phosphate, major and minor grooves) of a double-strand (ds) DNA, especially at atomic level. In the present study, we employ molecular dynamic (MD) simulations to investigate the binding of Cu2+ ions with the Dickerson DNA, a B-type dodecamer double stranded (ds) DNA. The binding characteristics of Cu2+ and Mg2+ ions with this dsDNA are compared to get an insight into the differences and similarities in binding behavior of both ions. Unlike Mg2+ ions, the first hydration shell of Cu2+ is found to be labile, thus it shows both direct and indirect binding with the dsDNA, i.e., binding through displacement of water from the hydration shell or through the hydration shell. Though the binding propensity of Cu2+ ions with dsDNA is observed relatively stronger, the binding order to phosphates, major groove, and minor groove is found qualitatively similar (phosphates > major groove > minor groove) for both ions. The study gives a deep understanding of Cu2+ binding to DNA, which could be helpful in rationalizing the Cu2+ led ROS-mediated DNA damage.

Quantitative proteomic analysis reveals Ga(III) polypyridyl catecholate complexes disrupt Aspergillus fumigatus mitochondrial function

Infections caused by the airborne fungal pathogen, Aspergillus fumigatus, are increasing in severity due to growing numbers of immunocompromised individuals and the increasing incidence of antifungal drug resistance, exacerbating treatment challenges. Gallium has proven to be a strong candidate in the fight against microbial pathogens due to its iron-mimicking capability and substitution of Ga(III) in place of Fe(III), disrupting iron-dependent pathways. Since the antimicrobial properties of 2,2'-bipyridine and derivatives have been previously reported, we assessed the in vitro activity and proteomic effects of a recently reported heteroleptic Ga(III) polypyridyl catecholate compound against A. fumigatus. This compound has demonstrated promising growth-inhibition and impact on the A. fumigatus proteome compared to untreated controls. Proteins associated with DNA replication and repair mechanisms along with lipid metabolism and the oxidative stress responses were elevated in abundance compared to control. Crucially, a large number of mitochondrial proteins were reduced in abundance. Respiration is an important source of energy to fuel metabolic processes required for growth, survival and virulence, the disruption of which may be a viable strategy for the treatment of microbial infections.

NAIRDB: a database of Fourier transform infrared (FTIR) data for nucleic acids

The Nucleic Acid InfraRed Data Bank (NAIRDB) serves as a comprehensive public repository dedicated to the archival and free distribution of Fourier transform infrared (FTIR) spectral data specific to nucleic acids. This database encompasses a collection of FTIR spectra covering diverse nucleic acid molecules, including DNA, RNA, DNA/RNA hybrids and their various derivatives. NAIRDB covers details of the experimental conditions for FTIR measurements, literature links, primary sequence data, information about experimentally determined structures for related nucleic acid molecules and/or computationally modeled 3D structures. All entries undergo expert validation and curation to maintain the completeness, consistency and quality of the data. NAIRDB can be searched by similarity of nucleic acid sequences or by direct comparison of spectra. The database is open for the submission of the FTIR data for nucleic acids. NAIRDB is available at https://nairdb.genesilico.pl.

Thermodynamics and Kinetics-Directed Regulation of Nucleic Acid-Based Molecular Recognition

Nucleic acid-based molecular recognition plays crucial roles in various fields like biosensing and disease diagnostics. To achieve optimal detection and analysis, it is essential to regulate the response performance of nucleic acid probes or switches to match specific application requirements by regulating thermodynamics and kinetics properties. However, the impacts of thermodynamics and kinetics theories on recognition performance are sometimes obscure and the relative conclusions are not intuitive. To promote the thorough understanding and rational utilization of thermodynamics and kinetics theories, this review focuses on the landmarks and recent advances of nucleic acid thermodynamics and kinetics and summarizes the nucleic acid thermodynamics and kinetics-based strategies for regulation of nucleic acid-based molecular recognition. This work hopes such a review can provide reference and guidance for the development and optimization of nucleic acid probes and switches in the future, as well as for advancements in other nucleic acid-related fields.

Interplay of heavy metal accumulation, physiological responses, and microbiome dynamics in lichens: insights and future directions

Lichens are increasingly recognised as valuable bioindicators for environmental heavy metal pollution due to their sensitivity to spatial and temporal variations in pollution levels and their ability to adapt to diverse and often harsh habitats. This review initially examines the mechanisms of metal absorption in lichens, including particulate entrapment, ion exchange, and intracellular absorption, as well as their physiological responses to abiotic stressors such as heavy metal exposure and desiccation. In the latter part, we compile and synthesise evidence showing that secondary metabolites in lichens are significantly influenced by metal concentrations, with varying impacts across different species. Although extensive research has addressed the broader physiological effects of heavy metal hyperaccumulation in lichens, there remains a significant gap in understanding the direct or indirect influences of heavy metals on the lichen microbiome, possibly mediated by changes in secondary metabolite production. Our review integrates these aspects to propose new research directions aimed at elucidating the mechanisms underlying physiological responses such as resilience and adaptability in lichens. Overall, this review highlights the dynamic interplay between microbiome composition, secondary metabolite variation, and metal accumulation, suggesting that these factors collectively contribute to the physiological responses of lichens in polluted environments.

Anti-cancer property and DNA binding interaction of first row transition metal complexes: A decade update

Metal ions carry out a wide variety of functions, including acid-base/redox catalysis, structural functions, signaling, and electron transport. Understanding the interactions of transition metal complexes with biomacromolecules is essential for biology, medicinal chemistry, and the production of synthetic metalloenzymes. After the coincidental discovery of cisplatin, importance of the metal complexes in biochemistry became a top priority for inquiry. In this review, a decade update on various synthetic strategies to first row transition metal complex and their interaction with DNA through non-covalent binding are explored. Moreover, this effort provides an excellent analysis on the efficacy of theoretical and practical approaches to the systematic generation of new non-platinum based metallodrugs for anti-cancer therapeutics.

Evaluation of metal ions and DNA recovery from the surface of fired and unfired brass ammunition to improve STR profiling

Interest in recovering DNA from the surface of ammunition evidence for genotyping has increased over the past few years. Numerous studies have examined a variety of methods to maximize DNA recovery from these types of challenging samples, but successful DNA profiling has been inconsistent. Low amounts of DNA and PCR inhibition due to metal ions have been suggested as the leading causes of poor results; however, no study quantitatively examined the presence of metal ions at various stages of the DNA analysis workflow from DNA collection through to amplification. In this study, the effectiveness of six different DNA collection and purification methods commonly used by forensic laboratories to process brass ammunition for DNA evidence was investigated. The amount of copper, zinc, and other metals co-recovered from fired and unfired brass casings during DNA collection (using numerous soaking, swabbing, and direct PCR protocols) was quantified via Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES). This same panel of metals was subsequently quantified after DNA lysis and purification steps. Results demonstrated that low amounts of DNA, DNA damage, and degradation are more detrimental to STR typing results than PCR inhibition, as metal ions were successfully removed by all DNA purification methods tested. Furthermore, the use of metal ion chelators increased the amount of DNA recovered and number of reportable STR alleles. This research informs the forensic community on the most effective way to collect and process trace amounts of biological material from brass ammunition and similar evidence.

Development of an aptasensor for dibutyl phthalate detection and the elucidation of assay inhibition factors

We developed a fluorescence aptasensor (hereafter 'SG-aptasensor') using SYBR Green I, a newly truncated 20-mer aptamer, and probe DNA to detect dibutyl phthalate (DBP). The detection range of DBP was 0.1-100 ng L-1 with 0.08 ng L-1 as the limit of detection. To adapt the assay to environmental samples in the near future, possible inhibition factors (experimental and environmental) have been tested and reported. The experimental inhibitors included the incubation time, temperature, pH, and ionic strength. Consequently, temperature (2-25 °C) and pH (7.0-9.0) ranges did not significantly inhibit the assay. The incubation time required for sufficient reaction was at least 4 h, and a relative humidity <20% may have induced fluorescence quenching. Tris-HCl-based incubation buffer with excess ionic strength (more than 0.2 M NaCl) demonstrated an abnormal increase in fluorescence. Environmental inhibitors including cations (Mg2+, Ca2+, and Cu2+) and humic acids were tested. The fluorescence signal was significantly reduced (∼99%) by 100 mM Cu2+ compared to that by 0 mM Cu2+. In contrast, the reduction in fluorescence signal was marginal (<15%) when Mg2+ or Ca2+ ions were present. Inhibition of the assay was observed (∼28%) in the presence of 100 mg L-1 humic acids.

Trace DNA and its persistence on various surfaces: A long term study investigating the influence of surface type and environmental conditions - Part one, metals

It is imperative for proper evidence triage that forensic biologists understand what kind of results to expect from certain evidence types submitted for DNA analysis. The persistence of trace DNA has been insufficiently investigated and there is little data available pertaining to the persistence of DNA in different environmental conditions and on different materials. The goal of this study is to increase the available data on this topic which would, in turn, help forensic biologists manage expectations when submitting specific evidence types for DNA testing. The work presented herein is a large-scale persistence project aimed to identify trends in the persistence of trace DNA and indicate how different environmental storage conditions and target surface characteristics influence the persistence of cellular and cell free DNA (cfDNA) over time. To eliminate variation within the experiment we used a proxy DNA deposit consisting of a synthetic fingerprint solution, cellular DNA, and/or cfDNA. Samples were collected and analysed from 7 metals over the course of 1 year (27 time points) under 3 different environmental storage conditions. The results of this experiment show that metal type greatly influences DNA persistence. For instance, copper exhibited an expected poor DNA persistence (up to 4 h) which a purification step did not help increase the DNA yield. Alternatively, DNA can persist for up to a year on lead at levels potentially high enough to allow for forensic DNA testing. Additionally, this study showed that the sample storage environment had no impact on DNA persistence in most cases. When considering DNA type, cfDNA was shown to persist for longer than cellular DNA and persistence as a whole appears to be better when DNA is deposited as mixtures over when deposited alone. Unsurprisingly, it can be expected that DNA recovery rates from trace deposits will decrease over time. However, DNA decay is highly dependent on the metal surface and extremely variable at short time points but slightly less variable as time since deposition increases. This data is intended to add to our understanding of DNA persistence and the factors which affect it.

Intermolecular hydrogen bonding in DNA base pairs interacting with different numbers of bare and hydrated Li+: NBO, QTAIM, and computational spectroscopic studies

In this study, the effect of different numbers of Li+ interacting with various sites of DNA base pairs (adenine-thymine (AT) and cytosine-guanine (GC)) on the base pair structures, the strength of hydrogen bonding between the bases, and spectroscopic properties (IR and absorption spectra) of the base pairs was investigated. Two quantum computational analyses, the natural bonding orbitals (NBO) and the quantum theory of atoms in molecules (QTAIM), were used to follow the change in the strength of hydrogen bonds between the bases in each pair. The type of base pair's site interacting with Li+ showed different effects on the change in the strength of the hydrogen bonds between the bases. The IR and absorption spectra of the lithiated base pairs were calculated and compared with those of bare base pairs. This comparison provided the changes in the spectra as a fingerprint for the structural identification of different lithiated base pairs. Also, the determination of the change in the strength of hydrogen bonds in the lithiated base pairs compared to their bare base pairs. In the other part of this study, the effect of the hydration of the attached Li+ in the structure of lithiated base pairs on the strength of their hydrogen bonds and spectra was investigated.

A wide survey of heavy metals-induced in-vitro DNA replication stress characterized by rate-limited replication

Heavy metals (HMs) are environmental pollutants that pose a threat to human health and have been accepted to cause various diseases, including cancer and developmental disorders. DNA replication stress has been identified to be associated with such diseases. However, the effect of HMs exclusively on DNA replication stress is still not well understood. In this study, DNA replication stress induced by thirteen HMs was assessed using a simplified in-vitro DNA replication model. Two parameters, Cte/Ctc reflecting the cycle threshold value alteration and Ke/Kc reflecting the linear phase slope change, were calculated based on the DNA replication amplification curve to evaluate the rate of exponential and linear phases. These parameters were used to detect the replication rate reflecting in-vitro DNA replication stress induced by tested HMs. According to the effective concentrations and rate-limiting degree, HMs were ranked as follows: Hg, Ce > Pb > Zn > Cr > Cd > Co > Fe > Mn, Cu, Bi, Sr, Ni. Additionally, EDTA could relieve the DNA replication stress induced by some HMs. In conclusion, this study highlights the potential danger of HMs themselves on DNA replication and provides new insight into the possible links between HMs and DNA replication-related diseases.

Nucleotide-based regenerated fiber production using salmon (Oncorhynchus keta) milt waste by solution spinning

The use of nucleic acid-derived fibers has not been developed in contrast to the traditional use of polysaccharide- and protein-based fibers in daily life. Salmon, Oncorhynchus keta, is an abundant fishery resource, and its milt contains a huge amount of DNA. Most of the milt is discarded because it degrades easily and is unsuitable for food consumption. DNA-based fibers are expected to possess functionality and mechanical strength because DNA is a polyanion with a high molecular weight. Here, using DNA extracted from the salmon milt, we produced nucleotide-based fibers. A solution spinning system was applied using ethanol as a coagulant. Adding the salt to the dope solution reduced the solubility of DNA, which was essential for the successful spinning of DNA-based fibers. The obtained fibers became insoluble in water by ultraviolet (UV) exposure. Fibril-like structures were detected on the fracture surface, and humidity influenced the conformational structure. This study focuses on the bulk-scale production of biodegradable DNA-based fibers. Therefore, it can be used not only for clothing and filters but also as a functional material to remove harmful pollutants released into the ocean, such as heavy metal ions and aromatic derivatives.

Toxic, genotoxic, mutagenic, and bioaccumulative effects of metal mixture from settleable particulate matter on American bullfrog tadpoles (Lithobates catesbeianus)

Amphibians are more susceptible to environmental stressors than other vertebrates due to their semipermeable skin and physiological adaptations to living in very specific microhabitats. Therefore, the aim of the present study was to investigate the effects of a metal mixture from settleable particulate matter (SePM) released from metallurgical industries on Lithobates catesbeianus tadpoles. Endpoints analyzed included metal bioconcentration, morphological (biometrical indices), hematological parameters (hemoglobin and blood cell count), and erythrocyte DNA damage (genotoxicity and mutagenicity). American bullfrog tadpoles (Gosner's stage 25) were kept under control condition (no contaminant addition) or exposed to a sub-lethal and environmentally relevant concentration (1 g.L-1) of SePM for 96 h. Tadpoles exposed to SePM exhibited elevated whole blood levels of Fe56, AL, Sn, Pb, Zn, Cr, Cu, Ti, Rb, V, Ce, La, Ag, As. SePM-exposed tadpoles showed a significant decrease in condition factor (12%) and increases in hepatosomatic index (25%), hemoglobin concentration (17%), and total leukocytes (82%), thrombocytes (90%), and monocytes (78%) abundance. In addition, exposed tadpoles showed higher MN and ENAs (340 and 140%, respectively) frequencies, and erythrocyte DNA damage with approximately 1.2- to 1.8-fold increases in comet parameters. Taken together, these results suggest that the multimetal mixture found in SePM is potentially genotoxic and mutagenic to L. catesbeianus tadpoles, induces stress associated with hematological changes, and negatively affects growth. Although such contamination occurs at sublethal levels, regulatory standards are needed to control the emission of SePM and protect amphibian populations.

Transport of double-stranded ribonucleic acids (dsRNA) and deoxyribonucleic acids (DNA) in sand and iron oxide-coated sand columns under varying solution chemistries

Assessing ecological risks associated with the use of genetically modified RNA interference crops demands an understanding of the fate of crop-released insecticidal double-stranded RNA (dsRNA) molecules in soils. We studied the adsorption of one dsRNA and two double-stranded DNA as model nucleic acids (NAs) during transport through sand- and iron oxide-coated sand (IOCS)-filled columns over a range of solution pH and ionic compositions. Consistent with NA-sand electrostatic repulsion, we observed only slight retention of NAs in sand columns. Conversely, pronounced NA retention in IOCS columns is consistent with strong and irreversible NA adsorption involving electrostatic attraction to and inner-sphere complex formation of NAs with iron oxide coatings. Adsorption of NAs to iron oxides revealed a fast and a slow kinetic adsorption regime, possibly caused by the excluded-area effect. Adsorption of NAs to sand and IOCS increased in the presence of dissolved Mg2+ and with increasing ionic strength, reflecting cation-bridging and screening of repulsive electrostatics, respectively. The co-solute phosphate and a pre-adsorbed dissolved organic matter isolate competitively suppressed dsRNA adsorption to IOCS. Similar adsorption characteristics of dsRNA and similarly sized DNA suggest that existing information on DNA adsorption to soil particles helps in predicting adsorption and fate of dsRNA molecules in soils.

3D-Printed Functional Hydrogel by DNA-Induced Biomineralization for Accelerated Diabetic Wound Healing

Chronic wounds in diabetic patients are challenging because their prolonged inflammation makes healing difficult, thus burdening patients, society, and health care systems. Customized dressing materials are needed to effectively treat such wounds that vary in shape and depth. The continuous development of 3D-printing technology along with artificial intelligence has increased the precision, versatility, and compatibility of various materials, thus providing the considerable potential to meet the abovementioned needs. Herein, functional 3D-printing inks comprising DNA from salmon sperm and DNA-induced biosilica inspired by marine sponges, are developed for the machine learning-based 3D-printing of wound dressings. The DNA and biomineralized silica are incorporated into hydrogel inks in a fast, facile manner. The 3D-printed wound dressing thus generates provided appropriate porosity, characterized by effective exudate and blood absorption at wound sites, and mechanical tunability indicated by good shape fidelity and printability during optimized 3D printing. Moreover, the DNA and biomineralized silica act as nanotherapeutics, enhancing the biological activity of the dressings in terms of reactive oxygen species scavenging, angiogenesis, and anti-inflammation activity, thereby accelerating acute and diabetic wound healing. These bioinspired 3D-printed hydrogels produce using a DNA-induced biomineralization strategy are an excellent functional platform for clinical applications in acute and chronic wound repair.

Spectrophotometric and nucleic acid-binding properties of halloysite clay nanotubes and kaolinite

Halloysite particles (HNTs) are naturally occurring aluminosilicate nanotubes of low toxicity that have shown great promise for drug and biomolecule delivery into human and animal cells. Kaolinite particles retain the same layered structure as HNT, but do not form nanotubes. In this study, the spectrophotometric and sedimentation properties of the two clays in aqueous solutions and their abilities to associate with both small and large nucleic acids have been investigated. Both clays scattered ultraviolet light strongly and this characteristic of HNT was not affected by either vacuum treatment to remove trapped gases or by sonication. Vacuum treatment increased the binding of small nucleic acids to HNT and this association was further enhanced by addition of divalent metal ions. By contrast, only small RNAs were bound efficiently by kaolinite in the presence of Mg²⁺ ions. Large linear double-stranded DNAs and circular plasmid DNAs bound poorly to kaolinite under all conditions, but these nucleic acids could form strong associations with HNT. Differences in binding data were largely consistent with measurements of the available surface areas of each clay. These results demonstrate that interactions with each clay are critically dependent on both the type and the conformation of each nucleic acid.

Recent Achievements in Electrochemical and Optical Nucleic Acids Based Detection of Metal Ions

Recently nucleic acids gained considerable attention as selective receptors of metal ions. This is because of the possibility of adjusting their sequences in new aptamers selection, as well as the convenience of elaborating new detection mechanisms. Such a flexibility allows for easy utilization of newly emerging nanomaterials for the development of detection devices. This, in turn, can significantly increase, e.g., analytical signal intensity, both optical and electrochemical, and the same can allow for obtaining exceptionally low detection limits and fast biosensor responses. All these properties, together with low power consumption, make nucleic acids biosensors perfect candidates as detection elements of fully automatic portable microfluidic devices. This review provides current progress in nucleic acids application in monitoring environmentally and clinically important metal ions in the electrochemical or optical manner. In addition, several examples of such biosensor applications in portable microfluidic devices are shown.

New ternary Fe(III)-8-hydroxyquinoline-reduced Schiff base complexes as selective anticancer drug candidates

Due to the growing prevalence of cancer diseases, new therapeutic options are urgently needed, and drugs based on metal ions other than platinum are alternatives with exciting possibilities. We report the synthesis, characterization and biological effect of mixed-ligand Fe(III)-aminophenolate complexes derived from salicylaldehyde and L-tryptophan with quinoline derivatives as co-ligands, namely 8-hydroxyquinoline (8HQ), [Fe(L)(8HQ)(H₂O)] (1) and its 5-cloro derivative (Cl8HQ), [Fe(L)(Cl8HQ)(H₂O)] (2). The complex bearing the aminophenolate and lacking the quinoline co-ligand, [Fe(L)(Cl)(H₂O)₂] (3), was prepared for comparison. The analytical and spectroscopic characterization revealed that 1 and 2 are octahedral Fe(III) complexes with the aminophenolate acting as a dianionic tridentate ligand and 8HQ co-ligands as bidentate chelates. Spectroscopic techniques and molecular docking studies were used to evaluate the ability of these complexes to bind bovine serum albumin (BSA) and calf thymus DNA. Complex 2 [Fe(L)(Cl8HQ)(H₂O)] was the one showing higher affinity for both biomolecules. Cell viability was assessed in breast, colorectal and bone human cancer cell lines. 1 and 2 were found to be more active than cisplatin in all cell lines tested. A non-tumoral fibroblast line (L929, mouse non-tumoral fibroblasts) was used to evaluate selectivity. The results evidence that 2 shows much higher selectivity than 1 in all cell lines tested, but particularly in bone cancer cells in which selectivity index (SI) values are 8.0 and 18.8 for 1 and 2, respectively.

Cationic Copolymer-Augmented DNA Hybridization Chain Reaction

Various DNA assembly techniques and structures have emerged with the continuous progress of DNA nanotechnology. DNA hybridization chain reaction (HCR) is a representative example owing to isothermal and enzyme-free features. However, HCR is time consuming and is inhibited by nucleases present in biological samples. Herein, we demonstrated that a cationic copolymer, poly(l-lysine)-graft-dextran (PLL-g-Dex), significantly facilitated HCR and increased its initiator sensitivity by 40-fold. PLL-g-Dex promoted the generation of HCR products with high molecular weight by accelerating the initiation and the subsequent growth steps of HCR. Moreover, PLL-g-Dex protected the HCR system from nucleases, permitting HCR in the presence of serum components. Addition of PLL-g-Dex is a universal and efficient strategy that does not require optimization of the reactor setup or DNA sequences, thus laying a solid foundation for the wider application of HCR.

The position of geochemical variables as causal co-factors of diseases of unknown aetiology

Abstract

The term diseases of unknown aetiology (DUA) or idiopathic diseases is used to describe diseases that are of uncertain or unknown cause or origin. Among plausible geoenvironmental co-factors in causation of DUA, this article focusses on the entry of trace elements, including metals and metalloids into humans, and their involvement in humoral and cellular immune responses, representing potentially toxic agents with implications as co-factors for certain DUA. Several trace elements/metals/metalloids (micronutrients) play vital roles as co-factors for essential enzymes and antioxidant molecules, thus, conferring protection against disease. However, inborn errors of trace element/metal/metalloid metabolisms can occur to produce toxicity, such as when there are basic defects in the element transport mechanism. Ultimately, it is the amount of trace element, metal or metalloid that is taken up, its mode of accumulation in human tissues, and related geomedical attributes such as the chemical form and bioavailability that decisively determine whether the exerted effects are toxic or beneficial. Several case descriptions of DUA that are common worldwide are given to illustrate our knowledge so far of how trace element/metal/metalloid interactions in the immune system may engender its dysregulation and be implicated as causal co-factors of DUA.

Article highlights

The importance of a proper understanding of geochemical perturbations in human metabolisms is emphasisedIt is proferred that such an understanding would aid greatly in the decipherment of diseases of unknown aetiology (DUA)The thesis presented may pave the way towards better diagnosis and therapy of DUA.

Speciomics as a concept involving chemical speciation and omics

The study of chemical speciation and the refinement and expansion of omics-based methods are both consolidated and highly active research fields. Although well established, such fields are extremely dynamic and are driven by the emergence of new strategies and improvements in instrumentation. In the case of omics-based studies, subareas including lipidomics, proteomics, metallomics, metabolomics and foodomics have emerged. Here, speciomics is being proposed as an "umbrella" term, that incorporates all of these subareas, to capture studies where the evaluation of chemical species is carried out using omics approaches. This paper contextualizes both speciomics and the speciome, and reviews omics applications used for species identification through examination of proteins, metalloproteins, metabolites, and nucleic acids. In addition, some implications from such studies and a perspective for future development of this area are provided. SIGNIFICANCE: The synergic effect between chemical speciation and omics is highlighted in this work, demonstrating an emerging area of research with a multitude of possibilities in terms of applications and further developments. This work not only defines and contextualizes speciomics and individual speciomes, but also demonstrates with some examples the great potential of this new interdisciplinary area of research.

The Multiple States of Environmental DNA and What Is Known about Their Persistence in Aquatic Environments

Increased use of environmental DNA (eDNA) analysis for indirect species detection has spurred the need to understand eDNA persistence in the environment. Understanding the persistence of eDNA is complex because it exists in a mixture of different states (e.g., dissolved, particle adsorbed, intracellular, and intraorganellar), and each state is expected to have a specific decay rate that depends on environmental parameters. Thus, improving knowledge about eDNA conversion rates between states and the reactions that degrade eDNA in different states is needed. Here, we focus on eukaryotic extraorganismal eDNA, outline how water chemistry and suspended mineral particles likely affect conversion among each eDNA state, and indicate how environmental parameters affect persistence of states in the water column. On the basis of deducing these controlling parameters, we synthesized the eDNA literature to assess whether we could already derive a general understanding of eDNA states persisting in the environment. However, we found that these parameters are often not being measured or reported when measured, and in many cases very few experimental data exist from which to draw conclusions. Therefore, further study of how environmental parameters affect eDNA state conversion and eDNA decay in aquatic environments is needed. We recommend analytic controls that can be used during the processing of water to assess potential losses of different eDNA states if all were present in a water sample, and we outline future experimental work that would help determine the dominant eDNA states in water.

Biomarkers for pollution in caged mussels from three reservoirs in Bulgaria: A pilot study

The mussel-watch concept was firstly proposed in 1975, which was later adopted by several international monitoring programs worldwide. However, for the very first time, a field experiment with caged mussels was performed in three reservoirs in Bulgaria to follow the harmful effects of sub-chronic pollution (30 days) of metals, trace, and macro-elements, as well as some organic toxicants, such as polybrominated diphenyl ethers and chlorinated paraffins. Therefore, we studied the biometric indices, histochemical lesions in the gills, biochemical changes in the digestive glands (antioxidant defense enzymes, such as catalase, glutathione reductase, and glutathione peroxidase; metabolic enzymes, such as lactate dehydrogenase, alanine aminotransferase, and aspartate aminotransferase, and the neurotransmitter cholinesterase), in addition to the DNA damage in the Chinese pond mussel, Sinanodonta woodiana (Lea, 1834) in Kardzhali, Studen Kladenets and Zhrebchevo reservoirs in Bulgaria. Significant correlation trends between the pollution levels, which we reported before, and the biomarker responses were established in the current paper. Overall, we found that both tested organs were susceptible to pollution-induced oxidative stress. The different alterations in the selected biomarkers in the caged mussels compared to the reference group were linked to the different kinds and levels of water pollution in the reservoirs, and also to the simultaneously conducted bioaccumulation studies.

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The effects of water pollution in caged mussels from three large dam reservoirs in Bulgaria were assessed.

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A cocktail of different inorganic and organic toxicants was measured both in waters and mussels for the first time.

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Different biomarker responses (cellular to individual) were also followed in gills and digestive glands of the transplants.

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Correlation trends between the pollution levels and the applied biological tools were established.

Effect of Mono- and Divalent Metal Ions on Current-Voltage Features of a λ-DNA Solution Electrically Driven in a Microfluidic Capillary

The interactions of DNA molecules and metal ions lead to changes in their configuration and conformation, which in turn influence the current characteristics of the solution as DNA molecules are translocated through a micro/nanofluidic channel and ultimately cause serious impacts on the practical applications of DNA/gene chips for precisely manipulating and studying the molecular properties of single DNA molecules. In this study, the current characteristics of λ-DNA solutions without or with metal ions (i.e., K⁺, Na⁺, Mg²⁺, and Ca²⁺) were experimentally investigated when they were transported through a 5 μm microcapillary under an external electric field with asymmetric electrodes. Experimental data indicated some meaningful results. First, the current-voltage relations of the metal ion solutions were all linear, while those of λ-DNA solutions without or with metal ions were all nonlinear and followed power functions, of which the indices were related to the type, valence, and mobility of ions. Furthermore, as the concentrations of metal ions increased, the power indices of the λ-DNA solutions with monovalent metal ions increased, while those of the λ-DNA solutions with divalent ions decreased. Finally, the main reasons for the current characteristics were theoretically attributed to two possible mechanisms: the polarizations on the asymmetric electrodes and the interactions between λ-DNA and metal ions. These findings are helpful for the design of new biomedical micro/nanofluidic sensors and labs on a chip for accurately manipulating single DNA molecules.

Directional migration propensity of calf thymus DNA in a gradient of metal ions

The migration propensity and spatially modulated surface deposition of calf thymus DNA have been reported in response to gradients of different monovalent and divalent ions.

Why Intermolecular Nitric Oxide (NO) Transfer? Exploring the Factors and Mechanistic Aspects of NO Transfer Reaction

Small molecule activation & their transfer reactions in biological or catalytic reactions are greatly influenced by the metal-centers and the ligand frameworks. Here, we report the metal-directed nitric oxide (NO)...

Touch DNA recovery from unfired and fired cartridges: Comparison of swabbing, tape lifting and soaking

Over the recent few years, several DNA collection techniques and methodologies have been published for the recovery of DNA from fired cartridge cases. In this study, swabbing, the DNA collection technique currently used in our jurisdiction (NSW, Australia), was compared with tape lifting and soaking to assess DNA recovery rates, DNA quality and profile quality. Brass .22LR and 9mmP cartridges were used as they are the most commonly encountered in our jurisdiction. The cartridges (n = 107) were loaded into cleaned firearm magazines by three volunteers of unknown shedder status, to mimic routine casework sample types. Half of the handled cartridges were fired whilst the other half were kept unfired. STR genotypes were produced at both 29 and 30 PCR cycles to evaluate which improved handler allele detection. DNA recovery rates showed that swabbing recovered significantly less DNA than tape lifting and soaking. Whilst there were no significant differences between tape lifting and soaking, tape lifting, on average, yielded more DNA than soaking. The calibre of ammunition had no influence on DNA recovery and in line with expectations, firing was found to decrease DNA recovery for all three sampling techniques. Assessment of DNA quality showed no evidence of PCR inhibition in any of the samples for this study. However, degradation indices showed that most samples were slightly to moderately degraded. Fewer handler alleles were detected from both fired tape lifted and soaked cartridges than unfired cartridges. Whilst 30 amplification cycles allowed for the detection of slightly more handler alleles, no statistically significant differences were found between 29 and 30 PCR cycles. Nonetheless, 50% of the profiles from unfired soaked cartridges that were non-uploadable after 29 cycles were uploadable after 30 cycles. Furthermore, 83% of profiles from unfired cartridges that were tape lifted were uploadable onto our jurisdiction's database at both 29 and 30 PCR cycles. All magazine controls, despite cleaning, contained some level of background DNA. Furthermore, increasing the number of PCR cycles to 30 also increased the detection of non-handler alleles in DNA profiles. Our results suggest tape lifting yields more uploadable profiles from unfired and fired cartridge cases than swabbing but also more adventitious (non-handler) alleles. However additional research will be needed to evaluate the full potential of this method.

X-ray photoemission studies of the interaction of metals and metal ions with DNA

X-ray Photoelectron Spectroscopy (XPS) has been used to study the interactions of heavy metal ions with DNA with some success. Surface sensitivity and selectivity of XPS are advantageous for identifying and characterizing the chemical and elemental structure of the DNA to metal interaction. This review summarizes the status of what amounts to a large part of the photoemission investigations of biomolecule interactions with metals and offers insight into the mechanism for heavy metal-bio interface interactions. Specifically, it is seen that metal interaction with DNA results in conformational changes in the DNA structure.

Factors and methods to modulate DNA hybridization kinetics

DNA oligonucleotides are widely used in a diverse range of research fields from analytical chemistry, molecular biology, nanotechnology to drug delivery. In these applications, DNA hybridization is often the most important enabling reaction. Achieving control over hybridization kinetics and a high yield of hybridized products is needed to ensure high-quality and reproducible results. Since DNA strands are highly negatively charged and can also fold upon itself to form various intramolecular structures, DNA hybridization needs to overcome these barriers. Nucleation and diffusion are two main kinetic limiting steps although their relative importance differs in different conditions. The effects of length and sequence, temperature, pH, salt concentration, cationic polymers, organic solvents, freezing and crowding agents are summarized in the context of overcoming these barriers. This article will help researchers in the biotechnology-related fields to better understand and control DNA hybridization, as well as provide a landscape for future work in simulation and experiment to optimize DNA hybridization systems.

Adsorption of double-stranded ribonucleic acids (dsRNA) to iron (oxyhydr-)oxide surfaces: comparative analysis of model dsRNA molecules and deoxyribonucleic acids (DNA)

Double-stranded ribonucleic acid (dsRNA) molecules are novel plant-incorporated protectants expressed in genetically modified RNA interference (RNAi) crops. Ecological risk assessment (ERA) of RNAi crops requires a heretofore-missing detailed understanding of dsRNA adsorption in soils, a key fate process. Herein, we systematically study the adsorption of a model dsRNA molecule and of two double-stranded deoxyribonucleic acid (DNA) molecules of varying lengths to three soil iron (oxyhydr-)oxides - goethite, lepidocrocite, and hematite - over a range of solution pH (4.5-10), ionic strength (I = 10-100 mM NaCl) and composition (0.5, 1, and 3 mM MgCl2) and in the absence and presence of phosphate (0.05-5 mM) as co-adsorbate. We hypothesized comparable adsorption characteristics of dsRNA and DNA based on their structural similarities. Consistently, the three nucleic acids (NAs) showed high adsorption affinities to the iron (oxyhydr-)oxides with decreasing adsorption in the order goethite, lepidocrocite, and hematite, likely reflecting a decrease in the hydroxyl group density and positive charges of the oxide surfaces in the same order. NA adsorption also decreased with increasing solution pH, consistent with weakening of NA electrostatic attraction to and inner-sphere complex formation with the iron (oxyhydr-)oxides surfaces as pH increased. Adsorbed NA concentrations increased with increasing I and in the presence of Mg2+, consistent with adsorbed NA molecules adopting more compact conformations. Strong NA-phosphate adsorption competition demonstrates that co-adsorbates need consideration in assessing dsRNA fate in soils. Comparable adsorption characteristics of dsRNA and DNA molecules to iron (oxyhydr-)oxides imply that information on DNA adsorption to soil particle surfaces can inform dsRNA ERA.

Polymorphic Pairing Configurations of Guanine and Cytosine at the Water-HOPG Interface

A series of nucleobases guanine (G) and cytosine (C) pairing configurations have been fabricated on highly oriented pyrolytic graphite (HOPG) surface by controlling the molar ratio of G and C in water solution. Watson-Crick (WC) base pairing governs the association of C and G nucleobases when the molar ratio of C/G is adjusted to 1:1. Nucleobase-rich is preferentially hydrogen-bonded to the sites exposed around WC motifs with the adjustment of the C/G molar ratio. At a higher C/G molar ratio imbalance, the pairing configurations depend on the combination of interspace and sites of hydrogen binding between G and C bases. The systematic analysis of the high-resolution STM images and DFT calculations reveal that hydrogen bonding plays a dominant role in the formation of these pairing configurations and that the competition between the priority and diversity of hydrogen-bonded configurations bonding between G and C is the key for the pairing structural polymorphism.

Functional Nucleic Acid Nanomaterials: Development, Properties, and Applications

Functional nucleic acid (FNA) nanotechnology is an interdisciplinary field between nucleic acid biochemistry and nanotechnology that focuses on the study of interactions between FNAs and nanomaterials and explores the particular advantages and applications of FNA nanomaterials. With the goal of building the next-generation biomaterials that combine the advantages of FNAs and nanomaterials, the interactions between FNAs and nanomaterials as well as FNA self-assembly technologies have established themselves as hot research areas, where the target recognition, response, and self-assembly ability, combined with the plasmon properties, stability, stimuli-response, and delivery potential of various nanomaterials can give rise to a variety of novel fascinating applications. As research on the structural and functional group features of FNAs and nanomaterials rapidly develops, many laboratories have reported numerous methods to construct FNA nanomaterials. In this Review, we first introduce some widely used FNAs and nanomaterials along with their classification, structure, and application features. Then we discuss the most successful methods employing FNAs and nanomaterials as elements for creating advanced FNA nanomaterials. Finally, we review the extensive applications of FNA nanomaterials in bioimaging, biosensing, biomedicine, and other important fields, with their own advantages and drawbacks, and provide our perspective about the issues and developing trends in FNA nanotechnology.

pH-dependent sedimentation of DNA in the presence of divalent, but not monovalent, metal ions

Precipitation of DNA is performed frequently in molecular biology laboratories for the purpose of purification and concentration of samples and also for transfer of DNA into cells. Metal ions are used to facilitate these processes, though their precise functions are not well characterized. In the current study we have investigated the precipitation of double-stranded DNA by group 1 and group 2 metal ions. Double-stranded DNAs were not sedimented efficiently by metals alone, even at high concentrations. Increasing the pH to 11 or higher caused strong DNA precipitation in the presence of the divalent group 2 metals magnesium, calcium, strontium and barium, but not group 1 metals. Group 2 sedimentation profiles were distinctly different from that of the transition metal zinc, which caused precipitation at pH 8. Analysis of DNAs recovered from precipitates formed with calcium revealed that structural integrity was retained and that sedimentation efficiency was largely size-independent above 400 bp. Several tests supported a model whereby single-stranded DNA regions formed by denaturation at high pH became bound by the divalent metal cations. Neutralization of negative surface charges reduced the repulsive forces between molecules, leading to formation of insoluble aggregates that could be further stabilized by cation bridging (ionic crosslinking).

A TD-DFT study of the excited dissociative electronic states of the DNA nucleobases bound to Li. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2021;244:118862. [PMID: 32927359 DOI: 10.1016/j.saa.2020.118862]

In this work, the first and second dissociative potential curves of adenineLi⁺ (ADLi⁺), guanineLi⁺ (GUALi⁺), cytosineLi⁺(CYTLi⁺), and thymineLi⁺ (THYLi⁺) complexes, related to the dissociation of their LiO and LiN bonds, have been calculated in the gas phase and water, separately. For this purpose, the fifteen excited potential curves, in order of increasing energy, were calculated for each complex and the dissociative potential curves were distinguished from them considering the conical intersection points. The time-dependent density functional theory (TD-DFT) method employing the M06-2X functional was used for the calculations. It was observed that the electron transfer from the DNA base to the Li⁺ took place during the dissociation of complexes in the gas phase. The electrostatic field of water blocked this charge transfer and led to the excited DNA base and Li⁺ in its ground state. The vertical excitation energy for the desorption of the Li fragment as a neutral and cation species from the DNA bases was determined. The effect of the interaction site of Li⁺ on the dissociative potential curves was also investigated.

The inorganic chemicals that surround us: role of tellurium, selenium and zinc on behavioural functions in mammals

Living organisms live in continuous interaction with its environment. During this process changes in one can induce adaptive responses on the other. Many factors in the environment have been studied with the notorious distinction of been rare or to be of high intensity strength in its interaction with living organisms. However, little attention has been put on some factors that have constant interaction with organisms but usually have low intensity strength, such as the case of the inorganic chemical environment that surrounds us. In this review, the interaction between the chemical element and living organisms is discussed under a theoretical model of interaction between compartments, giving attention to tellurium (Te), zinc (Zn) and selenium (Se) on some cognitive functions in human and animals. After studies in our laboratory of the phenotypic expression of the HSR (Hand Skill Relative) gene in school children community living in geographic zone rich in minerals and mines of La Rioja province, Argentine, where Te was found to be in higher non-toxic concentrations, a translational experimental model to maturing rats exposed to this trace element was made. Te was found to increase some parameters related to locomotion in an open field induced by novelty and exploratory motivation. At the same time, inhibition of lateralized responses, survival responses and social activity was also observed. Some of these changes, particularly those related to lateralization had similarity with that found previously in children of La Rioja province. Discussion of similarities and discrepancies of biologic effects between animals and humans, about the possible meaning of Te and its interaction with Zn and Se with relevance to humans was analyzed.

Regulating Catalytic Activity of DNA-Templated Silver Nanoclusters Based on their Differential Interactions with DNA Structures and Stimuli-Responsive Structural Transition

This work reports exquisite engineering of catalytic activity of DNA-templated silver nanoclusters (DNA-AgNCs) based on unique adsorption phenomena of DNAs on DNA-AgNCs and reversible transition between double and triple-stranded DNAs. Four DNA homopolymers exhibit different inhibition effects on the catalytic activity of DNA-AgNCs, poly adenine (polyA) > poly guanine (polyG) > poly cytosine (polyC) > poly thymine (polyT), demonstrating that polyA strands have the strongest adsorption affinity on DNA-AgNCs. Through the formation of T-A•T triplex DNAs, catalytic activity of DNA-AgNCs is restored from the deactivated state by double or single-stranded DNAs, indicating the participation of N7 groups of adenine bases in binding to DNA-AgNCs and blocking active sites. Accordingly, reversibly regulating catalytic activity of DNA-AgNCs can be realized based on DNA input-stimulated transition between duplex and triplex structures. In the end, two low-cost and facile biosensing methods are presented, which are derived from the activity-switchable platform. It is worthy to anticipate that the DNA-AgNCs with controlled catalytic activity will inspire researchers to devise more functionalized nanocatalysts and contribute to the exploration of intelligent biomedicine in the future.

Cu(ii) and V(iv)O complexes with tri- or tetradentate ligands based on (2-hydroxybenzyl)-l-alanines reveal promising anticancer therapeutic potential

New Cu^II- and V^IVO amino acid complexes show antiproliferative activity mediated by apoptosis and genomic damage.

Antimicrobial and antitumor activity of S-methyl dithiocarbazate Schiff base zinc(II) complexes

Schiff bases (SB) obtained from S-methyl dithiocarbazate and aromatic aldehydes: salicylaldehyde (H₂L¹), o-vanillin (H₂L²), pyridoxal (H₂L³) and 2,6-diformyl-4-methylphenol (H₃L⁴), and their corresponding Zn(II)-complexes (1-4), are synthesized. All compounds are characterized by elemental analyses, infrared, UV-Vis, nuclear magnetic resonance spectroscopy and mass spectrometry. The structures of H₂L² and [Zn₂(L¹)₂(H₂O)(DMF)] (1a) (DMF = dimethylformamide) are solved by single crystal X-ray diffraction. The SB coordinates the metal center through the O_phenolate, N_imine and S_thiolate atoms. The radical scavenging activity is tested using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, with all ligand precursors showing IC₅₀ values ~40 μM. Cytotoxicity studies with several tumor cell lines (PC-3, MCF-7 and Caco-2) as well as a non-tumoral cell line (NHDF) are reported. Interestingly, 1 has relevant and selective antiproliferative effect against Caco-2 cells (IC₅₀ = 9.1 μM). Their antimicrobial activity is evaluated in five bacterial strains (Klebsiella pneumoniae, Acinetobacter baumannii, Listeria monocytogenes, Pseudomonas aeruginosa and Staphylococcus aureus) and two yeast strains (Candida albicans and Candida tropicalis) with some compounds showing bacteriostatic and fungicidal activity. The minimal inhibitory concentration (MIC₉₀) of H_nL against Mycobacterium tuberculosis is also reported, with H₂L² and H₃L⁴ showing very high activity (MIC₉₀ < 0.6 μg/mL). The ability of the compounds to bind bovine serum albumin (BSA) and DNA is evaluated for H₃L⁴ and [Zn₂(L⁴)(CH₃COO)] (4), both showing high binding constants to BSA (ca. 10⁶ M^-1) and ability to bind DNA. Overall, the reported compounds show relevant antitumor and antimicrobial properties, our data indicating they may be promising compounds in several fields of medicinal chemistry.

Evaluation of the efficiency of Isohelix™ and Rayon swabs for recovery of DNA from metal surfaces

PURPOSE

We investigated the recovery and extraction efficiency of DNA from three metal surfaces (brass, copper, steel) relevant to forensic casework, and plastic (control) using two different swabbing systems; Rayon and Isohelix™ swabs, with sterile water and isopropyl alcohol respectively, as the wetting solutions.

METHODS

Twenty nanograms of human genomic DNA were applied directly to Isohelix™ and Rayon swabs; and to the metal and plastic substrates. All substrates were left to dry for 24 h, followed by single wet swabbing and extraction with the DNA IQ™ System. DNA extracts were quantified using real time quantitative PCR assays with SYBR green chemistry.

RESULTS

DNA was extracted from directly seeded Isohelix™ swabs with a high efficiency of 98%, indicating effective DNA-release from the swab into the extraction buffer. In contrast, only 58% of input DNA was recovered from seeded Rayon swabs, indicating higher DNA retention by these swabs. Isohelix™ swabs recovered 32 - 53% of DNA from metal surfaces, whilst the Rayon swabs recovered 11-29%. DNA recovery was lowest from copper and highest from brass. Interestingly, Rayon swabs appeared to collect more DNA from the plastic surface than Isohelix™ swabs, however, due to the lower release of DNA from Rayon swabs they returned less DNA overall following extraction than Isohelix™ swabs.

CONCLUSION

These results demonstrate that DNA samples deposited on metal surfaces can be more efficiently recovered using Isohelix™ swabs wetted with isopropyl alcohol than Rayon swabs wetted with sterile water, although recovery is affected by the substrate type.

The role of metal ion binding in the antioxidant mechanisms of reduced and oxidized glutathione in metal-mediated oxidative DNA damage

The antioxidant activity of glutathione in its reduced (GSH) and oxidized (GSSG) forms against metal-mediated oxidative DNA damage was studied by monitoring production of 8-hydroxy-2'-deoxyguanosine (8-OH-dG) from calf-thymus DNA. GSH and GSSG were combined with Fe(ii) and Cu(ii) before and after addition of DNA to investigate the role of metal coordination in the antioxidant mechanism. The antioxidant behavior of GSH and GSSG was also compared to the known radical scavenger DMSO. GSH and GSSG lower oxidative DNA damage for Fe(ii) and Cu(ii) reactions. GSH only exhibited appreciable antioxidant behavior when combined with Fe(ii) prior to adding DNA, and GSH and GSSG were slightly more effective against Cu(ii)-mediated damage when combined with Cu(ii) prior to adding DNA. Raman spectra of GSH in the presence of Cu(ii) indicate that Cu(ii) oxidizes GSH and raises the possibility that the antioxidant activity of GSH against Cu(ii) reactions may be attributed to its ability to form GSSG. No evidence of GSH oxidation in the presence of Fe(ii) was observed. The fluorescent probe dichlorofluorescein diacetate (DCF-DA) shows that the presence of GSH (for Cu(ii) reactions) and GSSG (for Fe(ii) and Cu(ii) reactions) lowers levels of reactive oxygen species (ROS) in bulk solution. Overall, the results suggest that the mechanism of antioxidant activity for GSH and GSSG against Fe(ii) and Cu(ii)-mediated oxidative damage involves metal coordination, and isothermal titration calorimetry (ITC) studies of the Cu(ii)-GSSG system show an enthalpically favored complexation reaction with an apparent 1 : 1 stoichiometry.

Are Titania Photocatalysts and Titanium Implants Safe? Review on the Toxicity of Titanium Compounds

Titanium and its compounds are broadly used in both industrial and domestic products, including jet engines, missiles, prostheses, implants, pigments, cosmetics, food, and photocatalysts for environmental purification and solar energy conversion. Although titanium/titania-containing materials are usually safe for human, animals and environment, increasing concerns on their negative impacts have been postulated. Accordingly, this review covers current knowledge on the toxicity of titania and titanium, in which the behaviour, bioavailability, mechanisms of action, and environmental impacts have been discussed in detail, considering both light and dark conditions. Consequently, the following conclusions have been drawn: (i) titania photocatalysts rarely cause health and environmental problems; (ii) despite the lack of proof, the possible carcinogenicity of titania powders to humans is considered by some authorities; (iii) titanium alloys, commonly applied as implant materials, possess a relatively low health risk; (iv) titania microparticles are less toxic than nanoparticles, independent of the means of exposure; (v) excessive accumulation of titanium in the environment cannot be ignored; (vi) titanium/titania-containing products should be clearly marked with health warning labels, especially for pregnant women and young children; (vi) a key knowledge gap is the lack of comprehensive data about the environmental content and the influence of titania/titanium on biodiversity and the ecological functioning of terrestrial and aquatic ecosystems.

DNA recovery from unfired and fired cartridge cases: A comparison of swabbing, tape lifting, vacuum filtration, and direct PCR

The ability to recover trace DNA from fired cartridge cases can help establish important leads regarding the handler of the ammunition. Over recent years, several DNA recovery techniques for fired ammunition have been published. Three techniques of significant interest include tape lifting, direct PCR, and vacuum filtration. This study aimed to compare these to the swabbing method currently employed in our jurisdiction. Brass and nickel cartridges of five different calibres were spiked with 20ng of saliva and subject to DNA collection using all four DNA recovery methods. Unfired and fired cartridges were tested to examine the effects of firing. Swabbing recovered a greater quantity of DNA than vacuum filtration while no significant differences were found between swabbing and tape-lifting. The calibre of ammunition had no effect on DNA recovery. Firing significantly reduced DNA yield from nickel cartridges, while unfired brass cartridges returned less DNA than unfired nickel cartridges. PCR inhibition was not observed in any samples, although degradation indices suggested that most samples were slightly or moderately degraded. Analysis of profiles showed that swabbing and tape lifting resulted in greater numbers of alleles from fired nickel and brass cartridges compared to direct PCR. Samples from nickel cartridges were found to have a greater number of uploadable profiles than samples from brass cartridges. In addition, three mixed profiles were obtained from the single source spiked cartridges as well as evidence of pre-existing DNA on uncleaned cartridges and contaminating alleles on cleaned cartridges. Our results suggest that tape-lifting can be a suitable alternative to swabbing, but that caution must be taken when interpreting profiles from fired cartridge cases as small amounts of DNA not associated with the handling of the cartridges may be present.