Presence Of Spermine Research Articles

Rapid detection of spermine by using a cost-effective carbon nanostructured aptasensor

Spermine is a polyamine that participates in ion channel regulation and cell proliferation. It is considered a biomarker for pancreatic cancer. In this study, a carbon nanostructure-based aptasensor has been developed to rapidly detect spermine in solution by relying on Förster resonance energy transfer (FRET). The FRET donor, carbon quantum dots (CDs), are bioconjugated to aptamers specific for spermine. CDs have an average diameter of 5.0 ± 2.5 nm and have the maximum fluorescence intensity emitting at 510 nm when excited at 400 nm. Due to the π-π* interaction between DNA-based aptamer and GO, a FRET quencher, CDs bioconjugated with aptamer (CDs-aptamer) can directly attach on the surface of GO, resulting in significant FRET quenching. In the presence of spermine, GO and CDs-Aptamer separate, and the fluorescence intensity of CDs is restored. The restored fluorescence intensity of CD-aptamer can be observed when the concentration of spermine increases from 0.1 to 250 nM. The sensing system in this study could be a cost-effective, user-friendly method to quickly detect spermine, a biomarker for pancreatic cancer.

New Method for Analyzing Tyramine by Spectrofluorimetry: Application to Fish

A new method for direct spectrofluorimetric analysis of tyramine in various fish samples was established. Low limits of detection (LOD) between 0.53 ng/mL and 1.40 ng/mL and limits of quantification (LOQ) between 1.76 ng/mL and 4.68 ng/mL were obtained. Also, low values of relative standard deviations (RSD) between 0.30 % and 0.58 % were obtained; confirming good reproducibility of our measurements. The application of this method to our samples allowed the detection of tyramine with satisfactory recovery rates between 93.68 % and 106.60 %. Interference studies with different biogenic amines have shown that the determination of tyramine can be done without major problems in the presence of spermine, spermidine, and histamine. However, special attention should be paid when tyramine is determined in the presence of agmatine, cadaverine or putrescine. In all cases, the determination of tyramine is more influenced by the presence of tryptamine or dopamine in the sample.

Determination of urinary spermine using controlled dissolution of polysulfide modified gold electrode.

Spermine (SPM) is considered a biomarker for prostate cancer and detecting it becomes highly challenging due to its electro- and optical-inactive nature. SPM has a tendency to interact with groups such as phosphates and sulfides to form macrocyclic arrangements known as nuclear aggregates of polyamines. Using this tendency, an electrochemical sensor has been developed using apolysulfide (PS) modified Au electrode (PS@Au electrode). PS has been synthesized from elemental sulfur by hydrothermal method and characterized using UV-Vis, fluorescence, FTIR, SEM, and XPS analyses. The PS@Au electrode was employed for electrochemical sensing of SPM. In the presence of SPM, a decrease in gold oxide reduction current was noted which is proportional to the concentration of SPM. The decrease in gold oxide reduction (0.5V) current was attributed to the complexing nature of SPM-PS at the electrode interface. The reason for the decrease in current has been substantiated using XRF, XPS, and spectroelectrochemical studies. Under the optimized conditions, the PS@Au electrode exhibited a linear range of 1.55-250µM with LOD of 0.511 ± 0.02µM (3σ). The electrochemical strategy for SPM sensing exhibited better selectivity even in the presence of possible interferents. The selectivity stems from the selective interaction of SPM with PS on the Au electrode surface; the tested amino acids, and other molecules do not complex with PS and hence they could not interfere. The PS@Au electrode has been subjected to the determination of SPM in artificial urine samples and exhibited outstanding performance in the synthetic sample.

Elucidation of the Conformational Transition of Oligopeptidase B by an Integrative Approach Based on the Combination of X-ray, SAXS, and Essential Dynamics Sampling Simulation

Oligopeptidase B (OPB) is the least studied group from the prolyl oligopeptidase family. OPBs are found in bacteria and parasitic protozoa and represent pathogenesis factors of the corresponding infections. OPBs consist of two domains connected by a hinge region and have the characteristics of conformational dynamics, which include two types of movements: the bridging/separation of α/β-hydrolase catalytic and β-propeller-regulatory domains and the movement of a loop carrying catalytic histidine, which regulates an assembly/disassembly of the catalytic triad. In this work, an elucidation of the interdomain dynamics of OPB from Serratia proteamaculans (SpOPB) with and without modification of the hinge region was performed using a combination of X-ray diffraction analysis and small-angle X-ray scattering, which was complemented with an essential dynamics sampling (EDS) simulation. The first crystal structure of catalytically deficient SpOPB (SpOPBS532A) with an intact hinge sequence is reported. Similarly to SpOPB with modified hinges, SpOPBS532A was crystallized in the presence of spermine and adopted an intermediate conformation in the crystal lattice. Despite the similarity of the crystal structures, a difference in the catalytic triad residue arrangement was detected, which explained the inhibitory effect of the hinge modification. The SpOPBS532A structure reconstituted to the wild-type form was used as a starting point to the classical MD followed by EDS simulation, which allowed us to simulate the domain separation and the transition of the enzyme from the intermediate to open conformation. The obtained open state model was in good agreement with the experimental SAXS data.

Availability of polyamines affects virulence and survival of Neisseria meningitidis.

Neisseria meningitidis is a Gram-negative human-restricted pathogen that asymptomatically resides in the human respiratory tract. Meningococcal meningitis and sepsis both are caused by N. meningitidis. The bacterium must adhere to host epithelial cells in order to colonize effectively. The factors that determine the initial attachment to the host and dispersal, are not well understood. Metabolites released by the host may aid in meningococcal colonization and dissemination. Polyamines are aliphatic polycations that assist in cell survival and proliferation. The virulence properties of N. meningitidis after exposure to polyamines were investigated. Adhesion to nasopharyngeal epithelial cells increased in the presence of spermine. Also, the relative expression of adhesin, pilE increased in the presence of spermine. Further, relative expression of ctrA, ctrB and lipB was upregulated in the presence of spermidine, indicating increased capsule formation. Upregulated capsule synthesis of N. meningitidis in the presence of spermidine allows it to survive in murine macrophages. The study suggests the importance of the extracellular pool of polyamines in promoting virulence in N. meningitidis.

A combination of a graphene quantum dots-cationic red dye donor-acceptor pair and cucurbit[7]uril as a supramolecular sensor for ultrasensitive detection of cancer biomarkers spermine and spermidine.

In a unique approach, the combination of a donor-acceptor pair of hydroxy graphene quantum dots (GQDs-OH) and a red-emissive donor-two-acceptor (D-2-A) type dye with pyridinium units (BPBP) and the well-known host cucurbit[7]uril (CB[7]) has been exploited as a supramolecular sensing assembly for the detection of cancer biomarkers spermine and spermidine in aqueous media at the sub-ppb level based on the affinity-driven exchange of guests from the CB[7] portal. In the binary conjugate, green fluorescent GQDs-OH transfers energy to trigger the emission of the dye BPBP and itself remains in the turn-off state. CB[7] withdraws the dye from the surface of GQDs-OH by strong host-guest interactions with its portal, making GQDs-OH fluoresce again to produce a ratiometric response. In the presence of spermine (SP) or spermidine (SPD), their strong affinity with CB[7] forces the ejection of the fluorophore to settle on the GQDs-OH surface, and the strong green emission of GQDs-OH turns off to device a supramolecular sensor for the detection of SP/SPD. The DFT studies revealed interesting excited-state charge-transfer conjugate formation between BPBP and GQDs leading to turn-on emission of the dye, and further supported the stronger binding modes of BPBP-CB[7], indicating the retrieval of the emission of GQDs. The assembly-disassembly based sensing mechanism was also established by Job's plot analysis, particle size analysis, zeta potential, time-resolved spectroscopy, ITC studies, microscopic studies, etc. The supramolecular sensing assembly is highly selective to SP and SPD, and showed nominal interference from other biogenic amines, amino acids, various metal ions, and anions. The limits of detection (LODs) were 0.1 ppb and 0.9 ppb for spermine and spermidine, respectively. The potential for the real-world application of this sensing assembly was demonstrated by spiking SP and SPD in human urine and blood serum with a high %recovery.

Development of a Redox-Sensitive Spermine Prodrug for the Potential Treatment of Snyder Robinson Syndrome.

Snyder Robinson Syndrome (SRS) is a rare disease associated with a defective spermine synthase gene and low intracellular spermine levels. In this study, a spermine replacement therapy was developed using a spermine prodrug that enters cells via the polyamine transport system. The prodrug was comprised of three components: a redox-sensitive quinone "trigger", a "trimethyl lock (TML)" aryl "release mechanism", and spermine. The presence of spermine in the design facilitated uptake by the polyamine transport system. The quinone-TML motifs provided a redox-sensitive agent, which upon intracellular reduction generated a hydroquinone, which underwent intramolecular cyclization to release free spermine and a lactone byproduct. Rewardingly, most SRS fibroblasts treated with the prodrug revealed a significant increase in intracellular spermine. Administering the spermine prodrug through feeding in a Drosophila model of SRS showed significant beneficial effects. In summary, a spermine prodrug is developed and provides a lead compound for future spermine replacement therapy experiments.

Identification of polyamine compounds and characterization of polyamine oxidase from sheep's brain tissue

The study included partially purified of polyamine oxidase (PAO) from sheep's brain tissue by dialysis and ion exchange chromatography using DEAE-cellulose techniques. Isoenzymes (I and II) were obtained with specific activities 3.876 and 2.856 units/ mg of protein and purification folds 11 and 8 times respectively compared with crude enzyme.The specific activity of PAO I was better than PAO II, thus we considered it for following studying. The optimal conditions were 40 C and pH=9. Some of properties of partially purified PAO I enzyme were studied and the specificity was found to be superior to the substrate, where it was given the highest activity when using spermidine. The results showed the presence of cupper ion at a concentration of 0.1437 mg / mL in PAO I using an atomic absorption. The presence of the coenzyme conjugate flavin adenine dinucleotide (FAD) was also detected by using UV-Vis spectrum from (325-430) nm. The inhibitory effect of carbamazepine on the activity of homozygous PAO I was studied, and it was found that there was a decrease in the activity of the enzyme at different inhibitor concentrations. The type of inhibition of the drug was also studied, and it was found non-competitive, and that the value of the inhibition constant Ki was 1.8 mM. The polyamines in the crude extract of Sheep's brain were diagnosed with HPLC technique, and the results of the analysis indicated the presence of spermine, spermidine, cadavarin, diamino propane and hexylamine as well as the presence of other polymines.

Long Tracts of Guanines Drive Aggregation of RNA G-Quadruplexes in the Presence of Spermine.

G-Quadruplexes (GQs) are compact, stable structures in DNA and RNA comprised of two or more tiers of quartets whose G-rich motif of tracts of two or more G's occurs commonly within genomes and transcriptomes. While thermodynamically stable in vitro, these structures remain difficult to study in vivo. One approach to understanding GQ in vivo behavior is to test whether conditions and molecules found in cells facilitate their folding. Polyamines are biogenic polycations that interact with RNA. Among common polyamines, spermine contains the highest charge and is found in eukaryotes, making it a good candidate for association with high-charge density nucleic acid structures like GQs. Using a variety of techniques, including ultraviolet-detected thermal denaturation, circular dichroism, size exclusion chromatography, and confocal microscopy, on an array of quadruplex sequence variants, we find that eukaryotic biological concentrations of spermine induce microaggregation of three-tiered G-rich sequences, but not of purely two-tiered structures, although higher spermine concentrations induce aggregation of even these. The formation of microaggregates can also be induced by addition of as little as a single G to a two-tiered structure; moreover, they form at biological temperatures, are sensitive to salt, and can form in the presence of at least some flanking sequence. Notably, GQ aggregation is not observed under prokaryotic-like conditions of no spermine and higher NaCl concentrations. The sequence, polyamine, and salt specificity of microaggregation reported herein have implications for the formation and stability of G-rich nucleic acid aggregates in vivo and for functional roles for understudied GQ sequences with only two quadruplex tiers.

A comparative study of structural and dynamical properties of bovine serum albumin in the presence of spermine

Bovine Serum Albumin (BSA) has many functions in plasma. Serum albumins function as a carrier for fatty acids, thyroid hormones, and steroids in the blood and are involved in stabilizing the volume of extracellular fluid. BSA is a polypeptide with 583 amino acids and a molecular weight of 66,463 Da. Polyamines have several roles in cell physiology; Such as protection against oxidative damage, gene expression, and protein synthesis. Spermine (as a polyamine) is present in all eukaryotic cells. Using the methods of spectroscopic, thermal denaturation, molecular docking, and molecular dynamics simulation, we were able to investigate the effect of spermine binding to BSA in Tris-HCl buffer with pH 7.4. By binding spermine to the BSA, the absorbance changed significantly at 280 nm. The addition of spermine alters the folding of BSA and regularly decreases intrinsic fluorescence intensity at temperatures 298 K and 308 K. The formation of the BSA-spermine complex was mainly by electrostatic interactions. According to the results, fluorescence quenching (Ksv) was static and revealed one binding site for spermine. Also, molecular dynamics simulation results demonstrated that spermine binds to BSA and due to the decrease in RMSD and RMSF and the increase in Tm, it can be said that spermine has a stabilizing effect on BSA.

Biogenic Amines Increase the Odds of Bacterial Vaginosis and Affect the Growth of and Lactic Acid Production by Vaginal Lactobacillus spp.

Bacterial vaginosis (BV) is the most common vaginal disorder of reproductive-aged women, yet its etiology remains enigmatic. One clinical symptom of BV, malodor, is linked to the microbial production of biogenic amines (BA). Using targeted liquid chromatography mass spectrometry, we analyzed 149 longitudinally collected vaginal samples to determine the in vivo concentrations of the most common BAs and then assessed their relationship to BV and effect upon the growth kinetics of axenically cultured vaginal Lactobacillus species. Increases in cadaverine, putrescine, and tyramine were associated with greater odds of women transitioning from L. crispatus-dominated vaginal microbiota to microbiota that have a paucity of Lactobacillus spp. and from Nugent scores of 0 to 3 to Nugent scores of 7 to 10, consistent with BV. Exposure to putrescine lengthened the lag time and/or slowed the growth of all vaginal Lactobacillus spp. except L. jensenii 62G. L. iners AB107's lag time was lengthened by cadaverine but reduced in the presence of spermidine and spermine. The growth rate of L. crispatus VPI 3199 was slowed by cadaverine and tyramine, and strain-specific responses to spermine and spermidine were observed. BAs were associated with reduced production of d- and l-lactic acid by vaginal Lactobacillus spp., and this effect was independent of their effect upon Lactobacillus species growth. The exceptions were higher levels of d- and l-lactic acid by two strains of L. crispatus when grown in the presence of spermine. Results of this study provide evidence of a direct impact of common biogenic amines on vaginal Lactobacillus spp.IMPORTANCELactobacillus spp. are credited with providing the primary defense against gynecological conditions, including BV, most notably through the acidification of the vaginal microenvironment, which results from their production of lactic acid. The microbial production of BAs has been hypothesized to play a mechanistic role in diminishing Lactobacillus species-mediated protection, enabling the colonization and outgrowth of diverse anaerobic bacterial species associated with BV. Here, we demonstrate that in vivo increases in the most commonly observed BAs are associated with a loss of Lactobacillus spp. and the development of BV, measured by Nugent score. Further, we show that BAs formed by amino acid decarboxylase enzymes negatively affect the growth of type strains of the most common vaginal Lactobacillus spp. and separately alter their production of lactic acid. These results suggest that BAs destabilize vaginal Lactobacillus spp. and play an important and direct role in diminishing their protection of the vaginal microenvironment.

Exploring the structural basis of conformational alterations of myoglobin in the presence of spermine through computational modeling, molecular dynamics simulations, and spectroscopy methods

Spermine as polyamines can have interaction with the myoglobin (Mb). The intent of this pondering to evaluate the impact of spermine on Mb properties, for example, the structure and thermal stability. For this analysis, the following approaches are employed. Thermodynamics, molecular dynamics (MD), and docking and the use of other spectroscopic procedures. The results of fluorescence spectroscopy and docking showed that binding spermine to Mb was spontaneous. Spermine quenched the fluorescence of Mb through the static quenching process. The thermal stability of Mb was incremented when the concentration of spermine increased. The CD spectra showed Mb’s secondary structure shift with a rise in β-sheet and a decrease in α-helicity Mb’s in spermine presence. Molecular docking and MD simulation outcomes demonstrate that electrostatic forces show a critical function in stabilizing of this complex, which is in conforming to spectroscopic results. Communicated by Ramaswamy H. Sarma

Screening of Conditions that Facilitate Crystallization of Oligopeptidase B from Serratia Proteamaculans by Differential Scanning Fluorimetry

Oligopeptidases B (OpdBs) are two-domain serine peptidases with trypsin-like substrate specificity belonging to the prolyl oligopeptidase family. These enzymes are involved in the pathogenesis of trypanosomiasis, leishmaniasis, other parasitic infections, and in some cases bacterial infections and are potential targets for the development of therapeutic anti-infective agents. Only two three-dimensional structures of enzymes of this class were determined. Both these enzymes were from protozoa, whereas the structures of bacterial OpdBs are unknown. Differential scanning fluorimetry (thermofluor) was used to increase the efficiency of screening of crystallization conditions of OpdB from the bacterium Serratia proteamaculans (PSP). It was found that low-molecular-weight polyamines can stabilize PSP in solution. A crystal of PSP, which was grown by the vapor-diffusion method in the presence of spermine, was used to collect the X-ray diffraction data set to 1.88 A resolution at the synchrotron radiation source in the National Research Centre “Kurchatov Institute.”

Spermine as a porcine pancreatic elastase activator: spectroscopic and molecular simulation studies

The aim of this study was to investigate the spermine effect on the thermal denaturation, conformation and activity of elastase at three temperatures of 303, 313 and 323 K in the Tris buffer, at pH 8.5, using UV–vis spectrophotometry, spectrofluorometry and circular dichroism as well as molecular docking and molecular simulation. The increased absorption of elastase in the presence of spermine suggested a change in the environment of tryptophan. It was found that under the influence of spermine, the emission intensity of elastase extremely was reduced, and the use of the Stern-Volmer equation showed that some static quenching had occurred. The thermodynamic parameters values (enthalpy and entropy) and the molecular docking technique also revealed that van der Waals forces or hydrogen bonding interactions played an important role in the binding process. The spermine–elastase complex formation led to increasing the value of the catalytic constant (kcat). So it could be considered as an activator. Slight changes were observed in the second structure of elastase (1.06% increase for the α-helix and 0.048% decrease the β-sheet) and the thermal stability effect. Molecular docking results also demonstrated that spermine could bind to porcine pancreatic elastase, and van der Waals forces or hydrogen bonding interactions played the major role in the binding process. Overall, our results showed that spermine could induce structural alterations in elastase, acting as a partial stabilizer and an activator for the enzyme.Communicated by Ramaswamy H. Sarma

Spermine as a possible endogenous allosteric activator of carboxypeptidase A: multispectroscopic and molecular simulation studies

Carboxypeptidase A (EC.3.4.17.1) is a zinc-containing proteolytic enzyme that removes the C-terminal amino acid from a peptide chain with the free carboxylate-terminal. In this study, the effect of spermine interaction on the structure and thermal stability of Carboxypeptidase A was investigated by ultraviolet − visible spectroscopy, fluorescence spectroscopy, circular dichroism, Kinetic measurement, molecular docking and simulation studies have also been followed at the pH of 7.5. The transition temperature of Carboxypeptidase A, as a criterion of protein thermal stability, in the presence of spermine was enhanced by increasing the concentration of spermine. The results of fluorescence intensity changes, at two temperatures of 308 and 318 K, also suggested that spermine had a great ability to quench the fluorescence of Carboxypeptidase A through the static quenching procedure. The thermodynamic parameters changes, including standard Gibbs free-energy, entropy and enthalpy, showed that the binding of spermine to Carboxypeptidase A was spontaneous and the hydrogen bonding and van der Waals interactions played a major role in stabilizing the Carboxypeptidase A–spermine complex. The changes in the content of the α-helix and the β-sheet of the Carboxypeptidase A with binding to spermine were shown by the CD spectra method. Further, kinetic studies revealed that by increasing concentration of spermine, the activity of Carboxypeptidase A was enhanced. Also, the docking study revealed that the hydrogen bonding and van der Waals interactions played a major role in stabilizing the Carboxypeptidase A–spermine complex. As a result, spermine could be considered as an activator and a stabilizer for Carboxypeptidase A.Communicated by Ramaswamy H. Sarma

Development of stable liquid formulations for oligonucleotides

Oligonucleotide-based therapeutics have been implemented as a new therapeutic modality in biotech industry, which offers the opportunity to develop formulation platforms for robust parenteral formulations. The aim of this study was to gain a better understanding of stabilizing/de-stabilizing effects of different formulation parameters on unconjugated and N-acetylgalactosamine (GalNAc) conjugated single stranded oligonucleotides with locked nucleic acid modifications (LNA SSO), as model oligonucleotides. Various buffer systems, pH levels and different excipients were evaluated to optimize conditions for LNA SSO in liquid formulations. LNA SSO were exposed to different temperature conditions, mechanical stress as well as oxidative conditions, and the maximum feasible LNA SSO concentrations regarding handling and processing were determined. Finally, options for terminal sterilization of LNA SSO were evaluated. Results show that the tested LNA SSO were most stable under slightly alkaline conditions. A decrease in viscosity was best accomplished in the presence of spermine and lysine. Heat treatment and gamma irradiation caused high levels of degradation of the LNA SSO. Crucial formulation parameters, as identified in this study, should contribute to a significant increase in future productivity in drug product development for single-stranded oligonucleotides.

Supramolecular Assembly of DNA-Phenanthrene Conjugates into Vesicles with Light-Harvesting Properties.

Vesicle-shaped supramolecular polymers are formed by self-assembly of a DNA duplex containing phenanthrene overhangs at both ends. In the presence of spermine, the phenanthrene overhangs act as sticky ends linking the DNA duplexes together. In aqueous solution, the assembly leads to vesicles with a diameter in the range of 50-200 nm. Fluorescence measurements show that the assembled phenanthrene units act as light-harvesting complexes and transfer absorbed energy to an acceptor, such as pyrene or Cy3, which can either be directly added to the polymer or attached via a complementary DNA strand. The presence of DNA in the nanostructures allows the construction of light-harvesting vesicles that are amenable to derivatization with different functional groups.

Spermine Condenses DNA, but Not RNA Duplexes

Interactions between the polyamine spermine and nucleic acids drive important cellular processes. Spermine condenses DNA and some RNAs, such as poly(rA):poly(rU). A large fraction of the spermine present in cells is bound to RNA but apparently does not condense it. Here, we study the effect of spermine binding to short duplex RNA and DNA, and compare our findings with predictions of molecular-dynamics simulations. When small numbers of spermine are introduced, RNA with a designed sequence containing a mixture of 14 GC pairs and 11 AU pairs resists condensation relative to DNA of an equivalent sequence or to 25 bp poly(rA):poly(rU) RNA. A comparison of wide-angle x-ray scattering profiles with simulation results suggests that spermine is sequestered deep within the major groove of mixed-sequence RNA. This prevents condensation by limiting opportunities to bridge to other molecules and stabilizes the RNA by locking it into a particular conformation. In contrast, for DNA, simulations suggest that spermine binds externally to the duplex, offering opportunities for intermolecular interaction. The goal of this study is to explain how RNA can remain soluble and available for interaction with other molecules in the cell despite the presence of spermine at concentrations high enough to precipitate DNA.

Exploring the thermal stability and activity of α-chymotrypsin in the presence of spermine

Polyamines such as spermine can have interaction with protein. The aim of the present study was to investigate how spermine could influence the structure, thermal stability, and the activity of α-chymotrypsin. Kinetics, thermodynamics, molecular dynamics (MD), and docking simulations studies were conducted to investigate the effect of spermine on the activity and structure of α-Chymotrypsin (α-Chy) in 50 mM Tris–HCl buffer, with the pH 8, using different spectroscopic techniques as well as molecular docking and MD simulations. The stability and activity of α-Chy were increased in the presence of spermine. The results of the kinetic study showed that the activity of spermine was increased. Enzyme activation was accompanied by changes on the α-Chy conformation. Fluorescence intensity changes showed dynamic quenching during spermine binding. The fluorescence quenching of the α-Chy suggested the more polar location of Trp residues. Near-UV and Far-UV circular dichroism studies also demonstrated the transfer of Trp, Phe, and Tyr residues to a more flexible environment. The increase in the absorption of α-Chy in the presence of spermine was as a result of the formation of spermine–α-Chy complex. Molecular docking results revealed the presence of one binding site with a negative value for the Gibbs free energy of the binding of spermine to α-Chy. Docking study also revealed that van der Waals interactions and hydrogen bonds played a major role in stabilizing the complex.

Can Changes in Temperature or Ionic Conditions Modify the DNA Organization in the Full Bacteriophage Capsid?

We compared four bacteriophage species, T5, λ, T7, and Φ29, to explore the possibilities of DNA reorganization in the capsid where the chain is highly concentrated and confined. First, we did not detect any change in DNA organization as a function of temperature between 20 to 40 °C. Second, the presence of spermine (4+) induces a significant enlargement of the typical size of the hexagonal domains in all phages. We interpret these changes as a reorganization of DNA by slight movements of defects in the structure, triggered by a partial screening of repulsive interactions. We did not detect any signal characteristic of a long-range chiral organization of the encapsidated DNA in the presence and in the absence of spermine.