Evolution of a centromeric satellite DNA and phylogeny of lacertid lizards.

1. The composition and phyletic distribution of a highly repetitive satellite DNA, isolated from Podarcis sicula, was studied. 2. This DNA was rich in adenine and thymine and displayed frequent adenine stretches. It was always located on the centromeric heterochromatin even in quite taxonomically distant species. 3. Southern blot hybridization of the Taq I satellite on various species of lacertid families showed a close affinity among Podarcis, Algyroides and Lacerta dugesii. 4. All the other taxa investigated did not seem to possess this repeated sequence.     

Relationships of lacertid lizards (Reptilia: Lacertidae) estimated from mitochondrial DNA sequences and morphology.

DNA sequences from parts of the 12S, 16S and cytochrome b mitochondrial genes, which totalled 1049 aligned base pairs, were used to estimate the relationships of 49 species of Lacertidae, including representatives of 19 out of the 23 recognized genera and 23 species of the paraphyletic genus Lacerta. These data were used, together with morphological information, to estimate the relationships within the family. Molecular evidence corroborates the monophyletic status of many genera and species groups originally based on morphology. It indicates that Psammodromus forms a clade with Gallotia, which is the sister taxon of all other lacertids. These comprise three units: the primarily Afrotropical armatured group; the largely Oriental Takydromus; and the west Palaearctic Lacerta and its derivatives, Podarcis and Algyroides. Morphology also supports the first three assemblages, but suggests that they are derived from a paraphyletic Lacerta. Within Lacerta and its allies, DNA sequence analysis corroborates the affinity of some members of each of the subgenera Lacerta s. str. and Timon, and of the L. saxicola group. It also supports the relationship of L. monticola, L. bonnali and L. horvathi, and suggests that the L. parva--L. fraasi clade and L. brandli are not related to Psammodromus Gallotia, as morphology indicates, but instead are associated respectively with the L. danfordi and L. saxicola groups. DNA sequence data provide additional evidence that the eastern Arabian ''Lacerta'' jayakari and ''L.'' cyanura are members of the armatured clade and also sister species. Our analysis supports an origin for present lacertids in west Eurasia. The armatured clade invaded Africa, probably in the mid-Miocene, spreading widely and evolving increasingly xeric-adapted forms, one lineage of which later moved back into the Palaearctic. ''Lacerta'' jayakari and ''L.'' cyanura are assigned to Omanosaura, Lutz and Mayer 1986. The name Gallotiinae Cano, Baez, Lopez-Jurado & Ortega, 1984 is available for the Gallotia-Psammodromus clade, Eremiainae Shcherbak 1975 for the armatured clade and Lacertinae for Lacerta, Podarcis and Algyroides. Two new subgenera of Lacerta are proposed here: Caucasilacerta for L. saxicola and its allies, and Parvilacerta for L. parva and L. fraasi.     

Experimental demonstration of T:(G:G:G:G):T hexad and T:A:A:T tetrad alignments within a DNA quadruplex stem

A template-based approach was used to design unprecedented architectural motifs into a known DNA framework. The structure formed by the sequence d(GCGGTTGGAT) in 0.1 M Na(+) solution has been determined using molecular dynamics simulations constrained by distance and dihedral restraints derived from NMR experiments. The molecular topology has been previously observed for the sequence d(GCGGTGGAT) (Webba da Silva, M. (2003) Biochemistry 42, 14356-65). Insertion of a single thymine into the double chain reversal formed by the segment GGTGG results in the unprecedented experimental demonstration of a T:(G:G:G:G):T hexad. The bi-stranded hexad results from the pairing alignment of two G(T-G) triads. Each triad results from recognition of the sheared edge of a guanine by the Watson-Crick edge of a thymine of the segment GGTTGG. The alignment is stabilized by base-stacking of the thymine to the sugar pucker of the preceding thymine. The latter is involved in formation of the T:A:A:T tetrad alignment by forming a hydrogen bond with the free amino proton of a Watson-Crick aligned A:A mispair. We have thus established that residues in double chain reversal loops linking juxtaposed tetrads of a quadruplex stem may facilitate formation of yet unknown hydrogen bond alignments. By employing a systematic approach analysis of sequence motifs appearing in double chain reversals, bridging tetrad layers should allow for the prediction of topologies and architectural motifs appearing in biologically relevant genomic regions.     

A dimeric RNA quadruplex architecture comprised of two G:G(:A):G:G(:A) hexads,G:G:G:G tetrads and UUUU loops

Using CD and NMR, we determined the structure of an RNA oligomer, r(GGAGGUUUUGGAGG) (R14), comprising two GGAGG segments joined by a UUUU segment. A modified quadruplex structure was observed for r(GGAGGUUUUGGAGG) in solution even in the absence of K(+). An unusually stable dimeric RNA quadruplex architecture formed from two strands of r(GGAGGUUUUGGAGG) at low K(+) concentration is reported here. In each strand of r(GGAGGUUUUGGAGG), two sets of successive turns in the GGAGG segments and turns at both ends of the UUUU loops drive four G-G steps to align in a parallel manner, a core with two stacked G-tetrads being formed. Two adenine bases bind to two edges of one G:G:G:G tetrad through the sheared G:A mismatch augmenting the tetrad into a G:G(:A):G:G(:A) hexad. Thus, one molecule of r(GGAGGUUUUGGAGG) folds into a modified quadruplex comprising a G:G:G:G tetrad, a UUUU double-chain reversal loop and a G:G(:A):G:G(:A) hexad. Two such molecules further associate by stacking through the dimeric hexad-hexad interface with a rotational symmetry. The ribose rings of most nucleotides take S (close to C2'-endo) puckering, which is unusual for an RNA. K(+) can increase the stability of this quadruplex structure; the number of bound K(+) was estimated from the results of the titration experiment. Besides G:G and G:A mismatches, a network of hydrogen bonds including O4'-NH(2) and C-H..O hydrogen bonds, and the extensive base stacking contribute to the high thermodynamic stability of R14. Our results could provide the stereochemical and thermodynamic basis for elucidating the biological role of the GGAGG-containing RNA segments abundantly existing in various RNAs. Relevance to quadruplex-mediated mRNA-FMRP binding and HIV-1 genome RNA dimerization is discussed.     

Retinol and retinyl esters: biochemistry and physiology: Thematic Review Series: Fat-Soluble Vitamins: Vitamin A

By definition, a vitamin is a substance that must be obtained regularly from the diet. Vitamin A must be acquired from the diet, but unlike most vitamins, it can also be stored within the body in relatively high levels. For humans living in developed nations or animals living in present-day vivariums, stored vitamin A concentrations can become relatively high, reaching levels that can protect against the adverse effects of insufficient vitamin A dietary intake for six months, or even much longer. The ability to accumulate vitamin A stores lessens the need for routinely consuming vitamin A in the diet, and this provides a selective advantage to the organism. The molecular processes that underlie this selective advantage include efficient mechanisms to acquire vitamin A from the diet, efficient and overlapping mechanisms for the transport of vitamin A in the circulation, a specific mechanism allowing for vitamin A storage, and a mechanism for mobilizing vitamin A from these stores in response to tissue needs. These processes are considered in this review.     

Intramolecular higher order packing of parallel quadruplexes comprising a G:G:G:G tetrad and a G(:A):G(:A):G(:A):G heptad of GGA triplet repeat DNA

GGA triplet repeats are widely dispersed throughout eukaryotic genomes and are frequently located within biologically important regions such as gene regulatory regions and recombination hot spot sites. We determined the structure of d(GGA)4 (12-mer) under physiological conditions and founded the formation of an intramolecular parallel quadruplex for the first time. Later, a similar architecture to that of the intramolecular parallel quadruplex was found for a telomere DNA in the crystalline state. Here, we have determined the structure of d(GGA)8 (24-mer) under physiological conditions. Two intramolecular parallel quadruplexes comprising a G:G:G:G tetrad and a G(:A):G(:A):G(:A):G heptad are formed in d(GGA)8. These quadruplexes are packed in a tail-to-tail manner. This is the first demonstration of the intramolecular higher order packing of quadruplexes at atomic resolution. K+ ions, but not Na+ ones, are critically required for the formation of this unique structure. The elucidated structure suggests the mechanisms underlying the biological events related to the GGA triplet repeat. Furthermore, in the light of the structure, the mode of the higher order packing of the telomere DNA is discussed.     

Phylogeny of Bembidion and related ground beetles (Coleoptera: Carabidae: Trechinae: Bembidiini: Bembidiina)

The phylogeny of the large genus Bembidion and related genera is inferred from four nuclear protein-coding genes (CAD, wingless, arginine kinase, and topoisomerase I), ribosomal DNA (28S and 18S), and the mitochondrial gene cytochrome oxidase I (COI). 230 of the more than 1200 species of Bembidion are sampled, as well as 26 species of five related genera, and 14 outgroups. Nuclear copies (numts) of COI were found sparsely scattered through sampled species. The resulting phylogeny, based upon individual gene analyses and combined analyses using maximum likelihood and parsimony, is very well supported at most nodes. Additional analyses explored the evidence, and corroborate the phylogeny. Seven analyses, each with one of the seven genes removed from the combined matrix, were also conducted, and yielded maximum likelihood bootstrap trees sharing over 92% of their nodes with the original, well-resolved bootstrap trees based on the complete set of seven genes. All key nodes were present in all seven analyses missing a single gene, indicating that support for these nodes comes from at least two genes. In addition, the inferred maximum likelihood tree based on the combined matrix is well-behaved and self-predicting, in that simulated evolution of sequences on the inferred tree under the inferred model of evolution yields a matrix from which all but one of the model tree's clades are recovered with bootstrap value >50, suggesting that internal branches in the tree may be of a length to yield sequences sufficient to allow their inference. All likelihood analyses were conducted under both a proportion-invariable plus gamma site-to-site rate variation model, as well as a simpler gamma model. The choice of model did not have a major effect on inferred phylogenies or their bootstrap values. The inferred phylogeny shows that Bembidarenas is not closely related to Bembidiina, and Phrypeus is likely distant as well; the remaining genera of Bembidiina form a monophyletic group. Lionepha, formerly considered a subgenus of Bembidion, is shown to be outside of the clade of Asaphidion+Bembidion, and is separated as its own genus. B. (Phyla) obtusum is quite isolated within Bembidion, and there is some evidence that the remaining Bembidion form a clade. Within Bembidion, there are three large clades that are well-supported, the Bembidion, Odontium, and Ocydromus Series. The Bembidion Series contains Bembidion (s. str.), Notaphus, Furcacampa, Emphanes, Trepanedoris, Diplocampa, and related Holarctic species; all species from South America, Australia, New Zealand; and most species from southern Africa and Madagascar. All species in South America, except for members of Notaphus and Nothocys, form a clade, the Antiperyphanes Complex, which has independently radiated into body forms and niches occupied by multiple, independent Northern-Hemisphere forms. All species from New Zealand, including Zecillenus, and Australian species formerly placed in Ananotaphus together form a clade. Bembidion (s. str.) and Cyclolopha are in a clade with the Old World, Southern Hemisphere lineages Notaphocampa, Sloanephila, and Omotaphus. The large subgenus Notaphus appears to have originated in South America, with all Northern Hemisphere Notaphus arising from within a south-temperate grade. All major variation in frontal furrows on the head is contained within the Bembidion Series. The Odontium Series contains subgenera Hirmoplataphus and Hydriomicrus, which together are the sister clade of Odontium, Bracteon, Ochthedromus, Pseudoperyphus, and Microserrullula. The very large Ocydromus Series, dominant in the Holarctic region, includes the Ocydromus Complex, with many subgenera, including Hypsipezum and Leuchydrium; the phylogeny within this group is notably at odds with the current classification. Also included in the Ocydromus Series are Nepha and Bembidionetolitzkya, as well as the Princidium Complex, in which the intertidal B. (Cillenus) laterale falls. Outside these three series are a number of smaller groups, including the Plataphus Complex (containing Blepharoplataphus, Plataphus, the latter including Plataphodes); the Hydrium Complex (Metallina, Chlorodium, and Hydrium, which contains Eurytrachelus), whose sister group might be subgenus Andrewesa; Trechonepha and Liocosmius, which might be sisters; and B. (Melomalus) planatum, which is not close to Plataphus. There is some evidence that these groups plus the Ocydromus and Odontium Series form a clade. A few enigmatic groups were harder to place. The sister group of the pair Philochthus plus Philochthemphanes might be B. wickhami; Eupetedromus is well outside the three major series and not related to Notaphus; the high-elevation Asian group Hoquedela is a very isolated lineage. Notaphiellus is removed from synonymy with Nothocys, and placed in synonymy with Notaphus; Plataphodes is synonymized with Plataphus, as Plataphus is paraphyletic otherwise; Eurytrachelus is synonymized with Hydrium. A new subgenus, Lindrochthus, is described to house the distinctive B. wickhami. The implications of the inferred phylogeny for some morphological characters used in Bembidiina systematics are explored, and some of the most widely used (e.g., location of discal seta ed3 on the elytron, and shape of the shoulder) are shown to be notably homoplastic. For example, the location of elytral seta ed3 has undergone at least nine transitions between two states.     

Assessment of heavy metal bioavailability using Escherichia coli zntAp::lux and copAp::lux-based biosensors

To determine the amount of metals detectable by bacteria, two plasmids were constructed in which the metal-inducible zntA and copA promoters from Escherichia coli were fused to a promoterless Vibrio fischeri luxCDABE operon. The luminescence response of E. coli bearing these constructs was studied as a function of the concentration of several heavy metals and was shown to be influenced by cell growth phase. The zntAp::lux fusion is induced mainly by salts of cadmium, lead, mercury and zinc, with significant induction by other metal ions, whereas the specificity of copA induction is restricted to copper and silver. In optimized assay conditions, metals could be detected at threshold concentrations ranging from nanomolar to micromolar, with maximal induction observed after only 60-100 min incubation. The ability of these biosensor strains to distinguish bioavailable quantities of metals in a sample makes them good candidates as useful tools to monitor metal contamination in environmental samples.     

Ultrastructure of the spermatozoon of Megaselia scalaris Loew (Diptera:Brachycera:Cyclorrhapha:Phoridea:Phoridae)

When viewed by scanning electron microscopy (SEM), the spermatozoon of the phorid dipteran Megaselia scalaris appears threadlike, lacking distinct head and tail areas. These areas can be observed, however, in appropriately stained material. Measurements of Feulgen-stained material reveal average lengths of the head, tail, and total cell of 18.7, 128.7, and 147.4 μm, respectively. When tested for sulfhydryl and disulfide groups, the head displays only disulfide groups. Transmission electron microscopy (TEM) reveals 12 different regions: three (1–3) in the head, four (9–12) in the tail, and five (4–8) in a short zone of overlap between the head and tail. Most of the cell lies in regions 9 and 11 of the tail and 3 of the head, accounting for, respectively, 37.3%, 45.7%, and 11.2% of the total length. A tubelike acrosome indents the anterior end of the nucleus. The tail originates asymmetrically in relation to the long axis of the cell as a peglike structure associated with the dorsolateral region of the nucleus. No centriole is visible, and the nucleus has a notched appearance in longitudinal sections. Two mitochondrial derivatives and an axoneme displaying a 9+9+2 microtubule configuration and ATPase activity extend throughout most of the tail. In regions 9 and 10, an asymmetrically arranged accessory body is also present. Features having possible taxonomic utility include the asymmetrically arranged accessory body, the size and shape of the acrosome, and the notched appearance of the nucleus. The present report is apparently the first to describe the spermatozoon of a cyclorrhaphous dipteran which is not a member of the Schizophora.     

Focus: Rare Disease: Chronic Pulmonary Aspergillosis: A Brief Review

Chronic Pulmonary Aspergillosis (CPA) is a destructive pulmonary disease caused by a fungal infection, affecting mainly individuals with prior or concurrent pulmonary conditions. It has a global prevalence of 42 per 100,000 population, but in the US and Europe, prevalence is less than 1 per 100,000. The clinical definition of CPA is based on various factors accounting for comorbidities, clinical presentation, and duration. It may be categorized into five subtypes that the disease may evolve between over time. Based on global consensus covering the spectrum of low-resource to high-resource settings, diagnosis is a multi-factorial process that involves a combination of clinical presentation persisting over 3 months, radiological findings, positive culture growth, and serological tests. CPA remains underdiagnosed due to a lack of awareness and is often misdiagnosed due to the comorbidities present. Treatment options are limited due to a lack of research. Furthermore, associated comorbidities and drug interactions further complicate treatment plans. Follow-up throughout treatment should be based on understanding the predictors of mortality. Identification of potential relapse or resistance to antifungal therapy is crucial to limit the low long-term survival rate. Awareness surrounding this devastating disease needs to be raised further to enable earlier identification, improve understanding of patient factors associated with prognosis, and the future potential for targeted therapies. This review aims to raise awareness of this rare condition among practitioners, by providing an overview of common risk factors influencing the prevalence and incidence of the disease. We further discuss current approaches and recent advancements in CPA diagnosis and treatment.     

Focus: Addiction: Case Report: Internet Gaming Disorder Associated With Pornography Use

Internet gaming disorder (IGD) is not currently a recognized diagnosis in the Diagnostic and Statistical Manual for Mental Disorders-5 (DSM-5). However, IGD has been noted to warrant further research for possible future inclusion in the DSM. In many ways, IGD strongly resembles substance and gambling addictions. Such characteristics include tolerance, withdrawal, and social and occupational neglect resulting from increased time invested in video game use and acquisition. The use of similar or closely related media is also seen, which mirrors the natural course of substance and gambling addictions. We present a case of a 22-year-old man who exhibited IGD and problems associated with pornography use. This case report exemplifies the sequelae of IGD. Our paper also reviews the possible mechanisms of behavioral addiction, as well as the status of IGD as a potential subcategory of behavioral addiction. Additional research is needed to determine if IGD co-occurs with problematic use of pornography.     

Quadruplexes of human telomere DNA analogs designed to contain G:A:G:A,G:G:A:A,and A:A:A:A tetrads

Replacement of two to four guanines by adenines in the human telomere DNA repeat dG₃(TTAG₃)₃ did not hinder the formation of quadruplexes if the substitutions took place in the terminal tetrad bridged by the diagonal loop of the intramolecular antiparallel three‐tetrad scaffold, as proved by CD and PAGE in both Na⁺ and K⁺ solutions. Thermodynamic data showed that, in Na⁺ solution, the dG₃(TTAG₃)₃ quadruplex was destabilized, the least by the two G:A:G:A tetrads, the most by the G:G:A:A tetrad in which the adenosines replaced syn‐guanosines. In physiological K⁺ solution, the highest destabilization was caused by the 4A tetrad. In K⁺, only the unmodified dG₃(TTAG₃)₃ quadruplex rearranged into a K⁺‐dependent quadruplex form, none of the multiple adenine‐modified structures did so. This may imply biological consequences for nonrepaired A‐for‐G mutations. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 880–886, 2010.     

Focus: Addiction: How Menthol Alters Tobacco-Smoking Behavior: A Biological Perspective

Mentholated cigarettes gained popularity in the 1950s and were often marketed as “healthy” cigarettes, attributable to their pleasurable mint flavor and cooling sensation in the mouth, lungs, and throat. While it is clear that nicotine is the primary psychoactive component in tobacco cigarettes, recent work has suggested that menthol may also play a role in exacerbating smoking behavior, despite original health claims. Recent evidence highlights four distinct biological mechanisms that can alter smoking behavior: 1) menthol acts to reduce the initially aversive experiences associated with tobacco smoking; 2) menthol can serve as a highly reinforcing sensory cue when associated with nicotine and promote smoking behavior; 3) menthol''s actions on nicotinic acetylcholine receptors may change the reinforcing value of nicotine; and 4) menthol can alter nicotine metabolism, thus increasing nicotine bioavailability. The purpose of this review is to highlight and evaluate potential biological mechanisms by which menthol can alter smoking behavior.     

A NEW SPECIES OF APROSTOCETUS FROM CHINA: (HYMENOPTERA: EULOPHIDAE: TETRASTICHINAE)

Abstract This paper deals with a new species of Aprostocetus collected from the campus of Jiangxi Agricultural University. This species is an inquiline living in the galls of a gall-midge on Ilex cornutu L. Specimens are preserved in the Department of Plant Protection, Jiangxi Agricultural University.     

Focus: Microbiome: Breathing Better Through Bugs: Asthma and the Microbiome

Asthma is a highly heterogeneous disease characterized by inflammation of the airways, which invokes symptoms such as wheeze, dyspnea, and chest tightness. Asthma is the product of multiple interconnected immunological processes and represents a constellation of related, but distinct, disease phenotypes. The prevalence of asthma has more than doubled since the 1980s, and efforts to understand this increase have inspired consideration of the microbiome as a key player in the pathophysiology and regulation of this disease. While recent years have seen an explosion of new research in this area, researchers are only beginning to untangle to mechanisms by which the microbiome may influence asthma. This review will focus on the relationship between the microbiome and the immune system and how this influences development of asthma. This review will also highlight evidence that may point the way toward new therapies and potential cures for this ancient respiratory foe.     

Discovering new insect viruses: whitefly iridovirus (Homoptera: Aleyrodidae: Bemisia tabaci)

Adult whiteflies, Bemisia tabaci (Gennadius), collected from the field were screened for viral pathogens using a cell line from the silverleaf whitefly, B. tabaci, B biotype (syn. B. argentifolii). Homogenates from the field-collected whiteflies were applied to cell cultures and checked for cytopathic effects (CPE). Cells were observed to develop cytoplasmic inclusions and to have a change in morphology. Cells displaying CPE were observed using a transmission electron microscope and found to be infected with a virus. The virus particles had an icosahedral shape and an approximate size of 120-130 nm. The virus was observed in defined areas of the cytoplasm adjacent to the cell nucleus. Analysis using polymerase chain reaction, Southern blot hybridization, and DNA sequencing confirmed that the virus discovered infecting the whitefly cell cultures was an iridovirus. Sequence analysis showed that the amplimer (893 bp) had a 95% homology to the invertebrate iridescent virus type 6 major capsid protein gene. Discovery of new viruses of whiteflies may provide renewed interest in using pathogens in the development of innovative management strategies. This is the first report of an iridescent virus isolated from whiteflies, B. tabaci, collected from the field.     

W::Neo: a novel dual-selection marker for high efficiency gene targeting in Drosophila

We have recently developed a so-called genomic engineering approach that allows for directed, efficient and versatile modifications of Drosophila genome by combining the homologous recombination (HR)-based gene targeting with site-specific DNA integration. In genomic engineering and several similar approaches, a "founder" knock-out line must be generated first through HR-based gene targeting, which can still be a potentially time and resource intensive process. To significantly improve the efficiency and success rate of HR-based gene targeting in Drosophila, we have generated a new dual-selection marker termed W::Neo, which is a direct fusion between proteins of eye color marker White (W) and neomycin resistance (Neo). In HR-based gene targeting experiments, mutants carrying W::Neo as the selection marker can be enriched as much as fifty times by taking advantage of the antibiotic selection in Drosophila larvae. We have successfully carried out three independent gene targeting experiments using the W::Neo to generate genomic engineering founder knock-out lines in Drosophila.     

An intramolecular quadruplex of (GGA)(4) triplet repeat DNA with a G:G:G:G tetrad and a G(:A):G(:A):G(:A):G heptad, and its dimeric interaction.

The structure of d(GGAGGAGGAGGA) containing four tandem repeats of a GGA triplet sequence has been determined under physiological K(+) conditions. d(GGAGGAGGAGGA) folds into an intramolecular quadruplex composed of a G:G:G:G tetrad and a G(:A):G(:A):G(:A):G heptad. Four G-G segments of d(GGAGGAGGAGGA) are aligned parallel with each other due to six successive turns of the main chain at each of the GGA and GAGG segments. Two quadruplexes form a dimer stabilized through a stacking interaction between the heptads of the two quadruplexes. Comparison of the structure of d(GGAGGAGGAGGA) with the reported structure of d(GGAGGAN) (N=G or T) containing two tandem repeats of the GGA triplet revealed that although the two structures resemble each other to some extent, the extension of the repeats of the GGA triplet leads to distinct structural differences: intramolecular quadruplex for 12-mer versus intermolecular quadruplex for 7-mer; heptad versus hexad in the quadruplex; and three sheared G:A base-pairs versus two sheared G:A base-pairs plus one A:A base-pair per quadruplex. It was also suggested that d(GGAGGAGGAGGA) forms a similar quadruplex under low salt concentration conditions. This is in contrast to the case of d(GGAGGAN) (N=G or T), which forms a duplex under low salt concentration conditions. On the basis of these results, the structure of naturally occurring GGA triplet repeat DNA is discussed.     

Mini-review: Lactoferrin: a bioinspired,anti-biofilm therapeutic

Medically relevant biofilms have gained a significant level of interest, in part because of the epidemic rise in obesity and an aging population in the developed world. The associated comorbidities of chronic wounds such as pressure ulcers, venous leg ulcers, and diabetic foot wounds remain recalcitrant to the therapies available currently. Development of chronicity in the wound is due primarily to an inability to complete the wound healing process owing to the presence of a bioburden, specifically bacterial biofilms. New therapies are clearly needed which specifically target biofilms. Lactoferrin is a multifaceted molecule of the innate immune system found primarily in milk. While further investigation is warranted to elucidate mechanisms of action, in vitro analyses of lactoferrin and its derivatives have demonstrated that these complex molecules are structurally and functionally well suited to address the heterogeneity of bacterial biofilms. In addition, use of lactoferrin and its derivatives has proven promising in the clinic.     

A minimal i-motif stabilized by minor groove G:T:G:T tetrads

The repetitive DNA sequences found at telomeres and centromeres play a crucial role in the structure and function of eukaryotic chromosomes. This role may be related to the tendency observed in many repetitive DNAs to adopt non-canonical structures. Although there is an increasing recognition of the importance of DNA quadruplexes in chromosome biology, the co-existence of different quadruplex-forming elements in the same DNA structure is still a matter of debate. Here we report the structural study of the oligonucleotide d(TCGTTTCGT) and its cyclic analog d<pTCGTTTCGTT>. Both sequences form dimeric quadruplex structures consisting of a minimal i-motif capped, at both ends, by a slipped minor groove-aligned G:T:G:T tetrad. These mini i-motifs, which do not exhibit the characteristic CD spectra of other i-motif structures, can be observed at neutral pH, although they are more stable under acidic conditions. This finding is particularly relevant since these oligonucleotide sequences do not contain contiguous cytosines. Importantly, these structures resemble the loop moiety adopted by an 11-nucleotide fragment of the conserved centromeric protein B (CENP-B) box motif, which is the binding site for the CENP-B.