The hydration structure of guanidinium and thiocyanate ions: implications for protein stability in aqueous solution

The interaction of thiocyanate with peptides-A computational study

According to the Hofmeister series, thiocyanate is the strongest "salting in" anion. In fact, it has a strong denaturant activity against the native state of globular proteins. A molecular level rationalization of the Hofmeister series is still missing, and therefore the denaturant activity of thiocyanate also awaits a robust explanation. In the last years, different types of experimental studies have shown that thiocyanate is capable to directly interact with both polar and nonpolar groups of polypeptide chains. This finding has been scrutinized via a careful computational procedure based on density functional theory approaches. The results indicate that thiocyanate is able to make H-bonds via both the nitrogen and sulfur atom, and to make strong van der Waals interactions with almost all the groups of polypeptide chains, regardless of their polarity.

NMR Dynamic View of the Stabilization of the WW4 Domain by Neutral NaCl and Kosmotropic Na2SO4 and NaH2PO4

The Hofmeister series categorizes ions based on their effects on protein stability, yet the microscopic mechanism remains a mystery. In this series, NaCl is neutral, Na2SO4 and Na2HPO4 are kosmotropic, while GdmCl and NaSCN are chaotropic. This study employs CD and NMR to investigate the effects of NaCl, Na2SO4, and Na2HPO4 on the conformation, stability, binding, and backbone dynamics (ps-ns and µs-ms time scales) of the WW4 domain with a high stability and accessible side chains at concentrations ≤ 200 mM. The results indicated that none of the three salts altered the conformation of WW4 or showed significant binding to the four aliphatic hydrophobic side chains. NaCl had no effect on its thermal stability, while Na2SO4 and Na2HPO4 enhanced the stability by ~5 °C. Interestingly, NaCl only weakly interacted with the Arg27 amide proton, whereas Na2SO4 bound to Arg27 and Phe31 amide protons with Kd of 32.7 and 41.6 mM, respectively. Na2HPO4, however, bound in a non-saturable manner to Trp9, His24, and Asn36 amide protons. While the three salts had negligible effects on ps-ns backbone dynamics, NaCl and Na2SO4 displayed no effect while Na2HPO4 significantly increased the µs-ms backbone dynamics. These findings, combined with our recent results with GdmCl and NaSCN, suggest a microscopic mechanism for the Hofmeister series. Additionally, the data revealed a lack of simple correlation between thermodynamic stability and backbone dynamics, most likely due to enthalpy-entropy compensation. Our study rationalizes the selection of chloride and phosphate as the primary anions in extracellular and intracellular spaces, as well as polyphosphate as a primitive chaperone in certain single-cell organisms.

NMR Dynamic View of the Destabilization of WW4 Domain by Chaotropic GdmCl and NaSCN

GdmCl and NaSCN are two strong chaotropic salts commonly used in protein folding and stability studies, but their microscopic mechanisms remain enigmatic. Here, by CD and NMR, we investigated their effects on conformations, stability, binding and backbone dynamics on ps-ns and µs-ms time scales of a 39-residue but well-folded WW4 domain at salt concentrations ≤200 mM. Up to 200 mM, both denaturants did not alter the tertiary packing of WW4, but GdmCl exerted more severe destabilization than NaSCN. Intriguingly, GdmCl had only weak binding to amide protons, while NaSCN showed extensive binding to both hydrophobic side chains and amide protons. Neither denaturant significantly affected the overall ps-ns backbone dynamics, but they distinctively altered µs-ms backbone dynamics. This study unveils that GdmCl and NaSCN destabilize a protein before the global unfolding occurs with differential binding properties and µs-ms backbone dynamics, implying the absence of a simple correlation between thermodynamic stability and backbone dynamics of WW4 at both ps-ns and µs-ms time scales.

Deciphering the guanidinium cation: Insights into thermal diffusion

Thermophoresis, or thermodiffusion, is becoming a more popular method for investigating the interactions between proteins and ligands due to its high sensitivity to the interactions between solutes and water. Despite its growing use, the intricate mechanisms behind thermodiffusion remain unclear. This gap in knowledge stems from the complexities of thermodiffusion in solvents that have specific interactions as well as the intricate nature of systems that include many components with both non-ionic and ionic groups. To deepen our understanding, we reduce complexity by conducting systematic studies on aqueous salt solutions. In this work, we focused on how guanidinium salt solutions behave in a temperature gradient, using thermal diffusion forced Rayleigh scattering experiments at temperatures ranging from 15 to 35 °C. We looked at the thermodiffusive behavior of four guanidinium salts (thiocyanate, iodide, chloride, and carbonate) in solutions with concentrations ranging from 1 to 3 mol/kg. The guanidinium cation is disk-shaped and is characterized by flat hydrophobic surfaces and three amine groups, which enable directional hydrogen bonding along the edges. We compare our results to the behavior of salts with spherical cations, such as sodium, potassium, and lithium. Our discussions are framed around how different salts are solvated, specifically in the context of the Hofmeister series, which ranks ions based on their effects on the solvation of proteins.

Super capacity of ligand-engineered biochar for sorption of malachite green dye: key role of functional moieties and mesoporous structure

This study synthesized a new thiomalic acid-modified rice husk biochar (TMA-BC) as a versatile and eco-friendly sorbent. After undergoing chemical treatments, the mercerized rice husk biochar (NaOH-BC) and TMA-BC samples showed higher BET surface area values of 277.1 m2/g and 305.8 m2/g, respectively, compared to the pristine biochar (BC) sample, which had a surface area of 234.2 m2/g. In batch adsorption experiments, it was found that the highest removal efficiency for malachite green (MG) was achieved with TMA-BC, reaching 96.4%, while NaOH-BC and BC exhibited removal efficiencies of 38.6% and 27.9%, respectively, at pH 8. The engineered TMA-BC exhibited a super adsorption capacity of 104.17 mg/g for MG dye at pH 8.0 and 25 °C with a dosage of 2 g/L. The SEM, TEM, XPS, and FTIR spectroscopy analyses were performed to examine mesoporous features and successful TMA-BC carboxylic and thiol functional groups grafting on biochar. Electrostatic forces, such as π - π interactions, hydrogen bonding, and pore intrusion, were identified as key factors in the sorption of MG dye. As compared to single-solution adsorption experiments, the binary solution experiments performed at optimized dosages of undesired ions, such as humic acid, sodium dodecyl sulfate surfactant, NaCl, and NaSCN, reflected an increase in MG dye removal of 2.8%, 8.7%, 5.4%, and 12.7%, respectively, which was attributed to unique mesoporous features and grafted functional groups of TMA-BC. Furthermore, the TMA-BC showed promising reusability up to three cycles. Our study indicates that mediocre biochar modified with TMA can provide an eco-friendly and cost-effective alternative to commercially accessible adsorbents.

Further treatment of coking wastewater treated in A2O-MBR by the nanofiltration-powder activated carbon hybrid system

In this study, further treatment of coking wastewater treated in anoxic-oxic-membrane bioreactor (A2O-MBR) was investigated to meet the standards of the ministry by means of nanofiltration (NF) (with two different membranes and different pressures), microfiltration -powder activated carbon (MF-PAC) hybrid system and NF-PAC (with two different membranes and five different PAC concentrations) hybrid system. In addition to the parameters determined by the ministry, other parameters such as ammonium, thiocyanate (SCN-), hydrogen cyanide (HCN), dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), color were also examined to evaluate the flux performance and treatment efficiency of the hybrid processes. According to the results, chemical oxygen demand (COD) in the NF process, COD and total cyanide (T-CN) in the MF-PAC process could not meet the discharge standards. As for the NF-PAC hybrid system, XN45 membrane met the discharge standards in all parameters (COD = 96±1.88 mg/L, T-CN =<0,02 mg/L, phenol =<0.05 mg/L), with a recovery rate of 78% at 0.5 g/L PAC concentration.

Stabilizing Decavanadate Cluster as Electrode Material in Sodium and Lithium-ion Batteries

Decavanadate ([V10 O28 ]6- , {V10 }) clusters are a potential electrode material for lithium and post-lithium batteries; however, their low stability due to the solubility in liquid organic electrolytes has been challenging. These molecular clusters are also prone to transform into solid-state oxides at a moderate temperature needed in the typical electrode fabrication process. Hence, controlling the solubility and improving the thermal stability of compounds are essential to make them more viable options for use as battery electrodes. This study shows a crystal engineering approach to stabilize the cluster with organic guanidinium (Gdm+ ) cation through the hydrogen-bonding interactions between the amino groups of the cation and the anion. The comparison of solubility and thermal stability of the Gdm{V10 } with another cluster bearing tetrabutylammonium (Tba+ ) cation reveals the better stability of cation-anion assembly in the former than the latter. As a result, the Gdm{V10 } delivers better rate capability and cycling stability than Tba{V10 } when tested as anode material in a half-cell configuration of a sodium-ion battery. Finally, the performance of the Gdm{V10 } anode is also investigated in a lithium-ion battery full cell with LiFePO4 cathode.

Shear-Enhanced Ion Rejection during Seawater Freezing

Ion rejection during seawater freezing is the basis for freeze desalination. A high ion rejection rate is desired for improving the performance of freeze desalination. In this work, we propose a method to enhance the ion rejection rate through external shear, which is demonstrated through molecular dynamics (MD) simulations and experiments. MD simulations show that the ion rejection rate increases with an increasing shear rate. This is attributed to the disruption of the hydration bonds between ions and water molecules in the hydration shell caused by the shear. Consequently, the mobility of ions is increased, and the energy barrier is reduced at the ice-water interface such that ions have a greater chance of diffusing into the aqueous solution, leading to an enhanced ion rejection rate. The MD results in this work are qualitatively confirmed by experiments and provide insights into the enhancement of the ion rejection rate through external parameters.

NAxtra magnetic nanoparticles for low-cost, efficient isolation of mammalian DNA and RNA

A cost-effective, viral nucleic acid (NA) isolation kit based on NAxtra magnetic nanoparticles was developed at the Norwegian University of Science and Technology in response to the shortage of commercial kits for isolation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA during the coronavirus disease 2019 (COVID-19) pandemic. This method showed comparable sensitivity to available kits at significantly reduced cost, making its application for other biological sources an intriguing prospect. Thus, based on this low-cost nucleic acid extraction technology, we developed a simple, low- and high-throughput, efficient method for isolation of high-integrity total NA, DNA and RNA from mammalian cell lines (monolayer) and organoids (3D-cultures). The extracted NA are compatible with downstream applications including (RT-)qPCR and next-generation sequencing. When automated, NA isolation can be performed in 14 min for up to 96 samples, yielding similar quantities to available kits.

Unique Properties of Nutrient Channels on Plasmodium-Infected Erythrocytes

Intracellular malaria parasites activate an ion and organic solute channel on their host erythrocyte membrane to acquire a broad range of essential nutrients. This plasmodial surface anion channel (PSAC) facilitates the uptake of sugars, amino acids, purines, some vitamins, and organic cations, but remarkably, it must exclude the small Na+ ion to preserve infected erythrocyte osmotic stability in plasma. Although molecular, biochemical, and structural studies have provided fundamental mechanistic insights about PSAC and advanced potent inhibitors as exciting antimalarial leads, important questions remain about how nutrients and ions are transported. Here, I review PSAC's unusual selectivity and conductance properties, which should guide future research into this important microbial ion channel.

Peptide/glycyrrhizic acid supramolecular polymer: An emerging medical adhesive for dural sealing and repairing

Medical adhesives have emerged as potential materials for sealing, hemostasis and wound repairing in modern clinical surgery. However, most of existing medical adhesives are still far away from the clinical requirements for simultaneously meeting desirable tissue adhesion, safety, biodegradability, anti-swelling property, and convenient operability. Here, we present an entirely new kind of peptide-based underwater adhesives, which are constructed via cross-linked supramolecular copolymerization between cationic short peptides and glycyrrhizic acid (GA) in an aqueous solution. We revealed the unique molecular mechanism of the peptide/GA supramolecular polymers and underlined the importance of arginine residues in the enhancement of the bulk cohesion of the peptide/GA adhesive. We thus concluded a design guideline that the peptide sequence has to be encoded with multiple arginine termini and hydrophobic residues. The resulting adhesives exhibited effective tissue adhesion, robust cohesion, low cell cytotoxicity, acceptable hemocompatibility, inappreciable inflammation response, appropriate biodegradability, and excellent anti-swelling property. More attractively, the dried peptide/GA powder was able to rapidly self-gel into adhesives by absorbing water, suggesting conveniently clinical operability. Animal experiments showed that the peptide/GA supramolecular polymers could be utilized as reliable medical adhesives for dural sealing and repairing.

Structural basis for ion selectivity in potassium-selective channelrhodopsins

KCR channelrhodopsins (K+-selective light-gated ion channels) have received attention as potential inhibitory optogenetic tools but more broadly pose a fundamental mystery regarding how their K+ selectivity is achieved. Here, we present 2.5-2.7 Å cryo-electron microscopy structures of HcKCR1 and HcKCR2 and of a structure-guided mutant with enhanced K+ selectivity. Structural, electrophysiological, computational, spectroscopic, and biochemical analyses reveal a distinctive mechanism for K+ selectivity; rather than forming the symmetrical filter of canonical K+ channels achieving both selectivity and dehydration, instead, three extracellular-vestibule residues within each monomer form a flexible asymmetric selectivity gate, while a distinct dehydration pathway extends intracellularly. Structural comparisons reveal a retinal-binding pocket that induces retinal rotation (accounting for HcKCR1/HcKCR2 spectral differences), and design of corresponding KCR variants with increased K+ selectivity (KALI-1/KALI-2) provides key advantages for optogenetic inhibition in vitro and in vivo. Thus, discovery of a mechanism for ion-channel K+ selectivity also provides a framework for next-generation optogenetics.

Categorization of hotspots into three types - weak, moderate and strong to distinguish protein-protein versus protein-peptide interactions

Protein-protein and protein-peptide interactions (PPI and PPepI) belong to a similar category of interactions, yet seemingly subtle differences exist among them. To characterize differences between protein-protein (PP) and protein-peptide (PPep) interactions, we have focussed on two important classes of residues-hotspot and anchor residues. Using implicit solvation-based free energy calculations, a very large-scale alanine scanning has been performed on benchmark datasets, consisting of over 5700 interface residues. The differences in the two categories are more pronounced, if the data were divided into three distinct types, namely - weak hotspots (having binding free energy loss upon Ala mutation, ΔΔG, ∼2-10 kcal/mol), moderate hotspots (ΔΔG, ∼10-20 kcal/mol) and strong hotspots (ΔΔG ≥ ∼20 kcal/mol). The analysis suggests that for PPI, weak hotspots are predominantly populated by polar and hydrophobic residues. The distribution shifts towards charged and polar residues for moderate hotspot and charged residues (principally Arg) are overwhelmingly present in the strong hotspot. On the other hand, in the PPepI dataset, the distribution shifts from predominantly hydrophobic and polar (in the weak type) to almost similar preference for polar, hydrophobic and charged residues (in moderate type) and finally the charged residue (Arg) and Trp are mostly occupied in the strong type. The preferred anchor residues in both categories are Arg, Tyr and Leu, possessing bulky side chain and which also strike a delicate balance between side chain flexibility and rigidity. The present knowledge should aid in effective design of biologics, by augmentation or disruption of PPIs with peptides or peptidomimetics.Communicated by Ramaswamy H. Sarma.

New insights into the protein stabilizing effects of trehalose by comparing with sucrose

Disaccharides are well known to be efficient stabilizers of proteins, for example in the case of lyophilization or cryopreservation. However, although all disaccharides seem to exhibit bioprotective and stabilizing properties, it is clear that trehalose is generally superior compared to other disaccharides. The aim of this study was to understand this by comparing how the structural and dynamical properties of aqueous trehalose and sucrose solutions influence the protein myoglobin (Mb). The structural studies were based on neutron and X-ray diffraction in combination with empirical potential structure refinement (EPSR) modeling, whereas the dynamical studies were based on quasielastic neutron scattering (QENS) and molecular dynamics (MD) simulations. The results show that the overall differences in the structure and dynamics of the two systems are small, but nevertheless there are some important differences which may explain the superior stabilizing effects of trehalose. It was found that in both systems the protein is preferentially hydrated by water, but that this effect is more pronounced for trehalose, i.e. trehalose forms less hydrogen bonds to the protein surface than sucrose. Furthermore, the rotational motion around dihedrals between the two glucose rings of trehalose is slower than in the case of the dihedrals between the glucose and fructose rings of sucrose. This leads to a less perturbed protein structure in the case of trehalose. The observations indicate that an aqueous environment closest to the protein molecules is beneficial for an efficient bioprotective solution.

Fifty years of gating currents and channel gating

We celebrate this year the 50th anniversary of the first electrophysiological recordings of the gating currents from voltage-dependent ion channels done in 1973. This retrospective tries to illustrate the context knowledge on channel gating and the impact gating-current recording had then, and how it continued to clarify concepts, elaborate new ideas, and steer the scientific debate in these 50 years. The notion of gating particles and gating currents was first put forward by Hodgkin and Huxley in 1952 as a necessary assumption for interpreting the voltage dependence of the Na and K conductances of the action potential. 20 years later, gating currents were actually recorded, and over the following decades have represented the most direct means of tracing the movement of the gating charges and gaining insights into the mechanisms of channel gating. Most work in the early years was focused on the gating currents from the Na and K channels as found in the squid giant axon. With channel cloning and expression on heterologous systems, other channels as well as voltage-dependent enzymes were investigated. Other approaches were also introduced (cysteine mutagenesis and labeling, site-directed fluorometry, cryo-EM crystallography, and molecular dynamics [MD] modeling) to provide an integrated and coherent view of voltage-dependent gating in biological macromolecules. The layout of this retrospective reflects the past 50 years of investigations on gating currents, first addressing studies done on Na and K channels and then on other voltage-gated channels and non-channel structures. The review closes with a brief overview of how the gating-charge/voltage-sensor movements are translated into pore opening and the pathologies associated with mutations targeting the structures involved with the gating currents.

The effect of denaturants on protein thermal stability analyzed through a theoretical model considering multiple binding sites

A novel mathematical development applied to protein ligand binding thermodynamics is proposed, which allows the simulation, and therefore the analysis of the effects of multiple and independent binding sites to the Native and/or Unfolded protein conformations, with different binding constant values. Protein stability is affected when it binds to a small number of high affinity ligands or to a high number of low affinity ligands. Differential scanning calorimetry (DSC) measures released or absorbed energy of thermally induced structural transitions of biomolecules. This paper presents the general theoretical development for the analysis of thermograms of proteins obtained for n-ligands bound to the native protein and m-ligands bound to their unfolded form. In particular, the effect of ligands with low affinity and with a high number of binding sites (n and/or m > 50) is analyzed. If the interaction with the native form of the protein is the one that predominates, they are considered stabilizers and if the binding with the unfolded species predominates, it is expected a destabilizing effect. The formalism presented here can be adapted to fitting routines in order to simultaneously obtain the unfolding energy and ligand binding energy of the protein. The effect of guanidinium chloride on bovine serum albumin thermal stability, was successfully analyzed with the model considering low number of middle affinity binding sites to the native state and a high number of weak binding sites to the unfolded state.

Guanidinium–amino acid hydrogen-bonding interactions in protein crystal structures: implications for guanidinium-induced protein denaturation

Structural analysis of guanidinium–amino acid interaction pairs in protein crystal structures is coupled with an effective scheme for classifying the optimized pairs, to gain understanding of the guanidinium:protein hydrogen bonding modes.

A Structure-Based Mechanism for the Denaturing Action of Urea, Guanidinium Ion and Thiocyanate Ion

An exhaustive analysis of all the protein structures deposited in the Protein Data Bank, here performed, has allowed the identification of hundredths of protein-bound urea molecules and the structural characterization of such binding sites. It emerged that, even though urea molecules are largely involved in hydrogen bonds with both backbone and side chains, they are also able to make van der Waals contacts with nonpolar moieties. As similar findings have also been previously reported for guanidinium and thiocyanate, this observation suggests that promiscuity is a general property of protein denaturants. Present data provide strong support for a mechanism based on the protein-denaturant direct interactions with a denaturant binding model to equal and independent sites. In this general framework, our investigations also highlight some interesting insights into the different denaturing power of urea compared to guanidinium/thiocyanate.

Non-specificity as the sticky problem in therapeutic antibody development

Antibodies are highly potent therapeutic scaffolds with more than a hundred different products approved on the market. Successful development of antibody-based drugs requires a trade-off between high target specificity and target binding affinity. In order to better understand this problem, we here review non-specific interactions and explore their fundamental physicochemical origins. We discuss the role of surface patches - clusters of surface-exposed amino acid residues with similar physicochemical properties - as inducers of non-specific interactions. These patches collectively drive interactions including dipole-dipole, π-stacking and hydrophobic interactions to complementary moieties. We elucidate links between these supramolecular assembly processes and macroscopic development issues, such as decreased physical stability and poor in vivo half-life. Finally, we highlight challenges and opportunities for optimizing protein binding specificity and minimizing non-specificity for future generations of therapeutics.

Confinement dependence of protein-associated solvent dynamics around different classes of proteins, from the EPR spin probe perspective

Protein function is modulated by coupled solvent fluctuations, subject to the degree of confinement from the surroundings. To identify universal features of the external confinement effect, the temperature dependence of the dynamics of protein-associated solvent over 200-265 K for proteins representative of different classes and sizes is characterized by using the rotational correlation time (detection bandwidth, 10-10-10-7 s) of the electron paramagnetic resonance (EPR, X-band) spin probe, TEMPOL, which is restricted to regions vicinal to protein in frozen aqueous solution. Weak (protein surrounded by aqueous-dimethylsulfoxide cryosolvent mesodomain) and strong (no added crysolvent) conditions of ice boundary confinement are imposed. The panel of soluble proteins represents large and small oligomeric (ethanolamine ammonia-lyase, 488 kDa; streptavidin, 52.8 kDa) and monomeric (myoglobin, 16.7 kDa) globular proteins, an intrinsically disordered protein (IDP, β-casein, 24.0 kDa), an unstructured peptide (protamine, 4.38 kDa) and a small peptide with partial backbone order (amyloid-β residues 1-16, 1.96 kDa). Expanded and condensate structures of β-casein and protamine are resolved by the spin probe under weak and strong confinement, respectively. At each confinement condition, the soluble globular proteins display common T-dependences of rotational correlation times and normalized weights, for two mobility components, protein-associated domain, PAD, and surrounding mesodomain. Strong confinement induces a detectable PAD component and emulation of globular protein T-dependence by the amyloid-β peptide. Confinement uniformly impacts soluble globular protein PAD dynamics, and is therefore a generic control parameter for modulation of soluble globular protein function.

Time-Dependent DNA Origami Denaturation by Guanidinium Chloride, Guanidinium Sulfate, and Guanidinium Thiocyanate

Guanidinium (Gdm) undergoes interactions with both hydrophilic and hydrophobic groups and, thus, is a highly potent denaturant of biomolecular structure. However, our molecular understanding of the interaction of Gdm with proteins and DNA is still rather limited. Here, we investigated the denaturation of DNA origami nanostructures by three Gdm salts, i.e., guanidinium chloride (GdmCl), guanidinium sulfate (Gdm₂SO₄), and guanidinium thiocyanate (GdmSCN), at different temperatures and in dependence of incubation time. Using DNA origami nanostructures as sensors that translate small molecular transitions into nanostructural changes, the denaturing effects of the Gdm salts were directly visualized by atomic force microscopy. GdmSCN was the most potent DNA denaturant, which caused complete DNA origami denaturation at 50 °C already at a concentration of 2 M. Under such harsh conditions, denaturation occurred within the first 15 min of Gdm exposure, whereas much slower kinetics were observed for the more weakly denaturing salt Gdm₂SO₄ at 25 °C. Lastly, we observed a novel non-monotonous temperature dependence of DNA origami denaturation in Gdm₂SO₄ with the fraction of intact nanostructures having an intermediate minimum at about 40 °C. Our results, thus, provide further insights into the highly complex Gdm–DNA interaction and underscore the importance of the counteranion species.

Development and application of LAMP assays for the detection of enteric adenoviruses in feces

Loop-mediated isothermal amplification (LAMP) is an alternative to PCR that is faster and requires fewer resources. Here, we describe two LAMP assays for the detection of human adenoviruses in the feces of children with acute intestinal infections. We designed сolorimetric LAMP (c-LAMP) and real-time LAMP (f-LAMP) with fluorescent probes to detect the DNA of the adenovirus F human adenovirus 40/41 (hAdV40/41) hexon gene. The detection limit of both developed methods was 10³ copies/mL, which is comparable to the sensitivity of PCR. The specificities of both c-LAMP and f-LAMP were high, with no false-positive results for clinical samples that do not contain adenovirus F, when testing other viruses and microorganisms. Comparative tests of PCR and LAMP on clinical samples from patients with acute gastroenteritis were carried out. For all samples with a PCR threshold cycle (C_T) of up to 36, the PCR and LAMP results completely coincided; however, at low viral loads, the diagnostic sensitivity of LAMP, especially c-LAMP with colorimetric detection, was inferior to that of PCR. The combination of LAMP with modern methods of nucleic acid extraction, both in manual and automatic modes, can reduce the time for a complete study, including extraction of nucleic acid material and amplification, to 60 min.

IMPORTANCE In April 2022, several cases of acute hepatitis of unknown origin were reported in children from 12 countries. In many cases, enteric adenovirus or SARS-CoV-2 and adenovirus coinfection were detected. It is known that human adenoviruses can cause different infections of varying severity, from asymptomatic to severe cases with lethal outcomes. There is a need to increase the diagnostic capabilities of clinical laboratories to identify such an underestimated pathogen as adenovirus. Although PCR remains the gold standard for pathogen detection, this method requires specialized equipment and has a long turnaround time to process samples. Previously, LAMP assays for the detection of human adenovirus have been based on measuring the turbidity, the fluorescence of intercalated dyes, or electrophoretic separation. Herein, we present LAMP-based assays with colorimetric or fluorescent detection and perform a detailed assessment of their sensitivity, specificity, and diagnostic performance.

Ionic group-dependent structure of complex coacervate hydrogels formed by ABA triblock copolymers

This study investigates the nanostructure of complex coacervate core hydrogels (C3Gs) with varying compositions of cationic charged groups (i.e., ammonium and guanidinium) using small-angle X-ray/neutron scattering (SAX/NS). C3Gs were prepared by stoichiometric mixing of two oppositely charged ABA triblock copolymers in aqueous solvents, in which A end-blocks were functionalized with either sulfonate groups or a mixture of ammonium and guanidinium groups. Comprehensive small-angle X-ray/neutron scattering (SAX/NS) analysis elucidated the dependence of C3Gs structures on the fraction of guanidinium groups in the cationic end-block (x) and salt concentration (c_s). As x increases, the polymer volume fraction in the cores, and interfacial tension (γ_core) and salt resistance (c*) of the coacervate cores increase, which is attributed to the greater hydrophobicity and non-electrostatic association. Furthermore, we observed that the salt dependence of the interfacial tension follows γ_core ∼ (1 - c_s/c*)^3/2 in all series of x. The results show that the variation of the ionic group provides a powerful method to control the salt-responsiveness of C3Gs as stimuli-responsive materials.

Direct Cytosolic Delivery of Proteins Using Lyophilized and Reconstituted Polymer-Protein Assemblies

PURPOSE

Cytosolic delivery of proteins accesses intracellular targets for chemotherapy and immunomodulation. Current delivery systems utilize inefficient endosomal pathways of uptake and escape that lead to degradation of delivered cargo. Cationic poly(oxanorbornene)imide (PONI) polymers enable highly efficient cytosolic delivery of co-engineered proteins, but aggregation and denaturation in solution limits shelf life. In the present study we evaluate polymer-protein nanocomposite vehicles as candidates for lyophilization and point-of-care resuspension to provide a transferrable technology for cytosolic protein delivery.

METHODS

Self-assembled nanocomposites of engineered poly(glutamate)-tagged (E-tagged) proteins and guanidinium-functionalized PONI homopolymers were generated, lyophilized, and stored for 2 weeks. After reconstitution and delivery, cytosolic access of E-tagged GFP cargo (GFPE15) was assessed through diffuse cytosolic and nuclear fluorescence, and cell killing with chemotherapeutic enzyme Granzyme A (GrAE10). Efficiency was quantified between freshly prepared and lyophilized samples.

RESULTS

Reconstituted nanocomposites retained key structural features of freshly prepared assemblies, with minimal loss of material. Cytosolic delivery (> 80% efficiency of freshly prepared nanocomposites) of GFPE15 was validated in several cell lines, with intracellular access validated and quantified through diffusion into the nucleus. Delivery of GrAE10 elicited significant tumorigenic cell death. Intracellular access of cytotoxic protein was validated through cell viability.

CONCLUSION

Reconstituted nanocomposites achieved efficient cytosolic delivery of protein cargo and demonstrated therapeutic applicability with delivery of GrAE10. Overall, this strategy represents a versatile and highly translatable method for cytosolic delivery of proteins.

Dendrimers as Antiamyloid Agents

Dendrimer-protein conjugates have significant prospects for biological applications. The complexation changes the biophysical behavior of both proteins and dendrimers. The dendrimers could influence the secondary structure of proteins, zeta-potential, distribution of charged regions on the surface, the protein-protein interactions, etc. These changes offer significant possibilities for the application of these features in nanotheranostics and biomedicine. Based on the dendrimer-protein interactions, several therapeutic applications of dendrimers have emerged. Thus, the formation of stable complexes retains the disordered proteins on the aggregation, which is especially important in neurodegenerative diseases. To clarify the origin of these properties and assess the efficiency of action, the mechanism of protein-dendrimer interaction and the nature and driving force of binding are considered in this review. The review outlines the antiamyloid activity of dendrimers and discusses the effect of dendrimer structures and external factors on their antiamyloid properties.

A Protein Data Bank survey of multimodal binding of thiocyanate to proteins: Evidence for thiocyanate promiscuity

Over the last one and half century, a myriad of studies has demonstrated that Hofmeister ions have a major impact on protein stability and solubility. Nevertheless, the definition of the physico-chemical basis of their activity has proved to be highly challenging and controversial. Here, by exploiting the enormous information content of the Protein Data Bank, we explored the binding to proteins of thiocyanate, the anion of the series exerting the highest solubilization/destabilization effects. The survey, which led to the identification and characterization of 712 thiocyanate binding sites, provides a comprehensive and atomic-level view of the varied interactions that the ion forms with proteins. The inspection of these sites highlights a limited tendency of thiocyanate to interact with structured water molecules, in line with the reported poor hydration of the ion. On the other hand, the thiocyanate makes interactions with protein nonpolar moieties, especially with the backbone C^α atom. In as many as 104 cases, the ion exclusively makes nonpolar contacts. In conclusion, these findings suggest that the ability of thiocyanate to bind all types of protein exposed patches may lead to the formation of a negatively charged electrostatic barrier that could prevent protein-protein aggregation and promote protein solubility. Moreover, the denaturing action of thiocyanate may be ascribed to its ability to establish multiple attractive interactions with protein surfaces.

Inorganic-Cation Pseudohalide 2D Cs2 Pb(SCN)2 Br2 Perovskite Single Crystal

Most of the reported 2D Ruddlesden-Popper (RP) lead halide perovskites with the general formula of A_{n +1} B_n X_{3 n +1} (n = 1, 2, …) comprise layered perovskites separated by A-site-substituted organic spacers. To date, only a small number of X-site-substituted RP perovskites have been reported. Herein, the first inorganic-cation pseudohalide 2D phase perovskite single crystal, Cs₂ Pb(SCN)₂ Br₂ , is reported. It is synthesized by the antisolvent vapor-assisted crystallization (AVC) method at room temperature. It exhibits a standard single-layer (n = 1) Ruddlesden-Popper structure described in space group of Pmmn (#59) and has a small separation (d = 1.69 Å) between the perovskite layers. The SCN^- anions are found to bend the 2D Pb(SCN)₂ Br₂ framework slightly into a kite-shaped octahedron, limiting the formation of a quasi-2D perovskite structure (n > 1). This 2D single crystal exhibits a reversible first-order phase transformation to 3D CsPbBr₃ (Pm3m #221) at 450 K. It has a low exciton binding energy of 160 meV-one of the lowest for 2D perovskites (n = 1). A Cs₂ Pb(SCN)₂ Br₂ -single-crystal photodetector is demonstrated with respectable responsivity of 8.46 mA W^-1 and detectivity of ≈1.2 × 10¹⁰ Jones at a low bias voltage of 0.5 V.

Clinical Evaluation of the Rapid STANDARD Q COVID-19 Ag Test for the Screening of Severe Acute Respiratory Syndrome Coronavirus 2

Standard tests for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) detect the presence of viral RNA using real-time reverse transcription (rRT)-PCR. Recently, convenient, rapid, and relatively inexpensive SARS-CoV-2 antigen (Ag) detection methods have been developed. The STANDARD Q COVID-19 Ag test (SD Biosensor, Inc., Suwon, Korea) is a rapid immunochromatography test that qualitatively detects the nucleocapsid protein of SARS-CoV-2 using gold conjugated antibodies. We evaluated its performance in comparison with that of Allplex 2019-nCoV Assay (Seegene, Seoul, Korea) in a retrospective case-control study using residual samples. The sensitivity and specificity of the STANDARD Q COVID-19 Ag test were 89.2% (58/65) and 96.0% (96/100), respectively. Cycle threshold (Ct) values for the three target SARS-CoV-2 genes (envelope, RNA-dependent RNA polymerase, and nucleocapsid genes) included in Allplex 2019-nCoV Assay were significantly lower in Ag test-positive patients than in Ag test-negative patients (P<0.001). The Ag test sensitivity was higher in samples with Ct≤30 and those collected one to five days post symptom onset. In conclusion, the STANDARD Q COVID-19 Ag test can serve as an alternative in high-prevalence settings, when the low sensitivity is compensated or when rRT-PCR tests are limited.

Arginine and Arginine-Rich Peptides as Modulators of Protein Aggregation and Cytotoxicity Associated With Alzheimer's Disease

A substantial body of evidence indicates cationic, arginine-rich peptides (CARPs) are effective therapeutic compounds for a range of neurodegenerative pathologies, with beneficial effects including the reduction of excitotoxic cell death and mitochondrial dysfunction. CARPs, therefore, represent an emergent class of promising neurotherapeutics with multimodal mechanisms of action. Arginine itself is a known chaotrope, able to prevent misfolding and aggregation of proteins. The putative role of proteopathies in chronic neurodegenerative diseases such as Alzheimer's disease (AD) warrants investigation into whether CARPs could also prevent the aggregation and cytotoxicity of amyloidogenic proteins, particularly amyloid-beta and tau. While monomeric arginine is well-established as an inhibitor of protein aggregation in solution, no studies have comprehensively discussed the anti-aggregatory properties of arginine and CARPs on proteins associated with neurodegenerative disease. Here, we review the structural, physicochemical, and self-associative properties of arginine and the guanidinium moiety, to explore the mechanisms underlying the modulation of protein aggregation by monomeric and multimeric arginine molecules. Arginine-rich peptide-based inhibitors of amyloid-beta and tau aggregation are discussed, as well as further modulatory roles which could reduce proteopathic cytotoxicity, in the context of therapeutic development for AD.

Protein- and Cell-Resistance of Zwitterionic Peptide-Based Self-Assembled Monolayers: Anti-Biofouling Tests and Surface Force Analysis

Peptide-based self-assembled monolayers (peptide-SAMs) with specific zwitterionic amino acid sequences express an anti-biofouling property. In this work, we performed protein adsorption and cell adhesion tests using peptide-SAMs with repeating units of various zwitterionic pairs of amino acids (EK, DK, ER, and DR). The SAMs with the repeating units of EK and DK (EK and DK SAMs) manifested excellent bioinertness, whereas the SAMs with the repeating units of ER and DR (ER and DR SAMs) adhered proteins and cells. We also performed surface force measurements using atomic force microscopy to elucidate the mechanism underlying the difference in the anti-biofouling property. Our measurements revealed that water-induced repulsion with a range of about 8 nm acts between EK SAMs (immobilized on both probe and substrate) and DK SAMs, whereas such repulsion was not observed for ER and DR SAMs. The strength of the repulsion exhibited a clear correlation with the protein- and cell-resistance of the SAMs, indicating that the interfacial water in the vicinity of EK and DK SAMs is considered as a physical barrier to deter protein and cells from their adsorption or adhesion. The range of the repulsion observed for EK and DK SAMs is longer than 8 nm, indicating that the hydrogen bonding state of the interfacial water with a thickness of 4 nm is modified by EK and DK SAMs, resulting in the expression of the anti-biofouling property.

Strong, Multifaceted Guanidinium-Based Adhesion of Bioorganic Nanoparticles to Wet Biological Tissue

Gluing dynamic, wet biological tissue is important in injury treatment yet difficult to achieve. Polymeric adhesives are inconvenient to handle due to rapid cross-linking and can raise biocompatibility concerns. Inorganic nanoparticles adhere weakly to wet surfaces. Herein, an aqueous suspension of guanidinium-functionalized chitin nanoparticles as a biomedical adhesive with biocompatible, hemostatic, and antibacterial properties is developed. It glues porcine skin up to 3000-fold more strongly (30 kPa) than inorganic nanoparticles at the same concentration and adheres at neutral pH, which is unachievable with mussel-inspired adhesives alone. The glue exhibits an instant adhesion (2 min) to fully wet surfaces, and the glued assembly endures one-week underwater immersion. The suspension is lowly viscous and stable, hence sprayable and convenient to store. A nanomechanic study reveals that guanidinium moieties are chaotropic, creating strong, multifaceted noncovalent bonds with proteins: salt bridges comprising ionic attraction and bidentate hydrogen bonding with acidic moieties, cation-π interactions with aromatic moieties, and hydrophobic interactions. The adhesion mechanism provides a blueprint for advanced tissue adhesives.

Probing Interfacial Effects on Ionization Energies: The Surprising Banality of Anion-Water Hydrogen Bonding at the Air/Water Interface

Liquid microjet photoelectron spectroscopy is an increasingly common technique to measure vertical ionization energies (VIEs) of aqueous solutes, but the interpretation of these experiments is subject to questions regarding sensitivity to bulk versus interfacial solvation environments. We have computed aqueous-phase VIEs for a set of inorganic anions, using a combination of molecular dynamics simulations and electronic structure calculations, with results that are in excellent agreement with experiment regardless of whether the simulation data are restricted to ions at the air/water interface or to those in bulk aqueous solution. Although the computed VIEs are sensitive to ion-water hydrogen bonding, we find that the short-range solvation structure is sufficiently similar in both environments that it proves impossible to discriminate between the two on the basis of the VIE, a conclusion that has important implications for the interpretation of liquid-phase photoelectron spectroscopy. More generally, analysis of the simulation data suggests that the surface activity of soft anions is largely a second or third solvation shell effect, arising from disruption of water-water hydrogen bonds and not from significant changes in first-shell anion-water hydrogen bonding.

General Counteraction Exerted by Sugars against Denaturants

The conformational stability of globular proteins is strongly influenced by the addition to water of different co-solutes. Some of the latter destabilize the native state, while others stabilize it. It is emerging that stabilizing agents are able to counteract the action of destabilizing agents. We have already provided experimental evidence that this counteraction is a general phenomenon and offered a rationalization. In the present work, we show that four different sugars, namely fructose, glucose, sucrose, and trehalose, counteract the effect of urea, tetramethylurea, sodium perchlorate, guanidinium chloride, and guanidinium thiocyanate despite the chemical and structural differences of those destabilizing agents. The rationalization we provide is as follows: (a) the solvent-excluded volume effect, a purely entropic effect, stabilizes the native state, whose solvent-accessible surface area is smaller than the one of denatured conformations; (b) the magnitude of the solvent-excluded volume effect increases markedly in ternary solutions because the experimental density of such solutions is larger than that of pure water.

Conformational Changes of Whey and Pea Proteins upon Emulsification Approached by Front-Surface Fluorescence

Proteins are widely used to stabilize emulsions, and plant proteins have raised increasing interest for this purpose. The interfacial and emulsifying properties of proteins depend largely on their molecular properties. We used fluorescence spectroscopy to characterize the conformation of food proteins from different biological origins (dairy or pea) and transformation processes (commercial or lab-made isolates) in solution and at the oil-water interface. The fourth derivative of fluorescence spectra provided insights in the local environment of tryptophan (Trp) residues and thus in the protein structure. In emulsions, whey proteins adsorbed with their Trp-rich region at the oil-water interface. Proteins in the commercial pea isolate were present as soluble aggregates, and no changes in the local environment of the Trp residues were detected upon emulsification, suggesting that these structures adsorb without conformational changes. The lab-purified pea proteins were less aggregated and a Trp-free region of the vicilin adsorbed at the oil-water interface.

Structures of (NaSCN)2(H2O)n -/0 (n = 0-7) and solvation induced ion pair separation: Gas phase anion photoelectron spectroscopy and theoretical calculations

We studied (NaSCN)₂(H₂O)_n ^- clusters in the gas phase using size-selected anion photoelectron spectroscopy. The photoelectron spectra and vertical detachment energies of (NaSCN)₂(H₂O)_n ^- (n = 0-5) were obtained in the experiment. The structures of (NaSCN)₂(H₂O)_n ^-/0 up to n = 7 were investigated with density functional theory calculations. Two series of peaks are observed in the spectra, indicating that two types of structures coexist, the high electron binding energy peaks correspond to the chain style structures, and the low electron binding energy peaks correspond to the Na-N-Na-N rhombic structures or their derivatives. For the (NaSCN)₂(H₂O)_n ^- clusters at n = 3-5, the Na-N-Na-N rhombic structures are the dominant structures, the rhombic four-membered rings start to open at n = 4, and the solvent separated ion pair (SSIP) type of structures start to appear at n = 6. For the neutral (NaSCN)₂(H₂O)_n clusters, the Na-N-Na-N rhombic isomers become the dominant starting at n = 3, and the SSIP type of structures start to appear at n = 5 and become dominant at n = 6. The structural evolution of (NaSCN)₂(H₂O)_n ^-/0 (n = 0-7) confirms the possible existence of ionic clusters such as Na(SCN)₂ ^- and Na₂(SCN)⁺ in NaSCN aqueous solutions.

High Efficiency RNA Extraction From Sperm Cells Using Guanidinium Thiocyanate Supplemented With Tris(2-Carboxyethyl)Phosphine

The extraction of high-quality ribonucleic acid (RNA) from tissues and cells is a key step in many biological assays. Guanidinium thiocyanate-phenol-chloroform (AGPC) is a widely used and efficient method to obtain pure RNA from most tissues and cells. However, it is not efficient with some cells like sperm cells because they are resistant to chaotropic lysis solutions containing guanidinium thiocyanate such as Buffer RLT+ and Trizol. Here, we show that disulfide bonds are responsible for the chemical resistance of sperm cells to RNA extraction reagents. We show that while β-mercaptoethanol (βME) can increase sperm lysis in Buffer RLT+, it has no effect in Trizol and leaves sperm cells intact. We measured the reduction of disulfide bonds in 2,2′-dithiodipyridine (DTDP) and observed that βME has a pH-dependent activity in chaotropic solutions, suggesting that pH is a limiting factor. We identified tris(2-carboxyethyl)phosphine (TCEP) as an efficient lysis enhancer of AGPC solutions that can retain reducing activity even at acidic pH. Trizol supplemented with TCEP allows the complete and rapid lysis of sperm cells, increasing RNA yield by 100-fold and resulting in RNA with optimal quality for reverse transcription and polymerase chain reaction. Our findings highlight the importance of efficient cell lysis and extraction of various macromolecules for bulk and single-cell assays, and can be applied to other lysis-resistant cells and vesicles, thereby optimizing the amount of required starting material and animals.

An ultrafast vibrational study of dynamical heterogeneity in the protic ionic liquid ethyl-ammonium nitrate. I. Room temperature dynamics

Using ultrafast two-dimensional infrared spectroscopy (2D-IR), a vibrational probe (thiocyanate, SCN^-) was used to investigate the hydrogen bonding network of the protic ionic liquid ethyl-ammonium nitrate (EAN) in comparison to H₂O. The 2D-IR experiments were performed in both parallel (⟨ZZZZ⟩) and perpendicular (⟨ZZXX⟩) polarizations at room temperature. In EAN, the non-Gaussian lineshape in the FTIR spectrum of SCN^- suggests two sub-ensembles. Vibrational relaxation rates extracted from the 2D-IR spectra provide evidence of the dynamical differences between the two sub-ensembles. We support the interpretation of two sub-ensembles with response function simulations of two overlapping bands with different vibrational relaxation rates and, otherwise, similar dynamics. The measured rates for spectral diffusion depend on polarization, indicating reorientation-induced spectral diffusion (RISD). A model of restricted molecular rotation (wobbling in a cone) fully describes the observed spectral diffusion in EAN. In H₂O, both RISD and structural spectral diffusion contribute with similar timescales. This complete characterization of the dynamics at room temperature provides the basis for the temperature-dependent measurements in Paper II of this series.

Rapid detection of SARS-CoV-2 by pulse-controlled amplification (PCA)

In the current pandemic of SARS-CoV-2, rapid identification of infected individuals is crucial for management and control of the outbreak. However, transport of samples, sample processing and RT-qPCR analysis in laboratories are time-consuming. Here we present a prototype of a novel nucleic acid-based test format - pulse controlled amplification - that allows detection of SARS-CoV-2 directly from up to eight swab samples simultaneously without the need for RNA extraction within 25 min with a sensitivity of 100 % for samples with a viral load of ≥ 1.6 × 10e3 copies/μl This new principle might pave the way to rapid and sensitive point of care testing.

Cationic Side Chain Identity Directs the Hydrophobically Driven Self-Assembly of Amphiphilic β-Peptides in Aqueous Solution

Hydrophobic interactions mediated by nonpolar molecular fragments in water are influenced by local chemical and physical contexts in ways that are not yet fully understood. Here, we use globally amphiphilic (GA) β-peptides (GA-Lys and GA-Arg) with stable conformations to explore if replacement of β³-homolysine (βLys) with β³-homoarginine (βArg) influences the hydrophobically driven assembly of these peptides in bulk aqueous solution. The studies were conducted in 10 mM triethanolamine buffer at pH 7, where both βLys (ammonium) and βArg (guanidinium) side chains are substantially protonated. Comparisons of light scattering measurements and cryo-electron micrographs before and after the addition of 60 vol% MeOH indicate very different outcomes of the hydrophobically driven assembly of AcY-GA-Lys versus AcY-GA-Arg (AcY denotes an N-acetylated-β³-homotyrosine (βTyr) at each N-terminus). Nuclear magnetic resonance and analytical ultracentrifugation confirm that AcY-GA-Lys assembles into large aggregates in aqueous buffer, whereas AcY-GA-Arg at comparable concentrations forms only small oligomers. Titration of AcY-GA-Arg into aqueous solutions of AcY-GA-Lys reveals that the driving force for AcY-GA-Lys association is far stronger than that for AcY-GA-Arg association. We discuss these results in the light of past experimental observations involving single molecule force measurements with GA β-peptides and hydrophobically driven dimerization of conventional peptides that form a GA α-helix upon dimerization (but do not display the Lys versus Arg trend predicted by extrapolating from the earlier AFM studies with β-peptides). Overall, our results establish that the identity of proximal cationic groups, ammonium versus guanidinium, profoundly modulates the hydrophobically driven self-assembly of conformationally stable β-peptides in bulk aqueous solution.

Methylguanidinium at the Air/Water Interface: A Simulation Study with the Drude Polarizable Force Field

Methylguanidinium is an important molecular ion, which also serves as the model compound for the arginine side chain. We studied the structure and dynamics of the methylguanidium ion at the air/water interface by molecular dynamics simulations employing the Drude polarizable force field. We found out that methylguanidinium accumulated at the interface, with a majority adopting tilted conformations. We also demonstrated that methylguanidinium and guanidinium ions had different preference toward the air/water interface. Detailed analysis of induced dipole moments showed how ions adjusted their charge distribution at the interface and revealed how the anisotropy in molecular polarizability impacted the orientation of molecular ions. Our results illustrate the importance of explicitly including the electronic polarization effects in modeling interfacial properties.

Indole, Phenyl, and Phenol Groups: The Role of the Comonomer on Gene Delivery in Guanidinium Containing Methacrylamide Terpolymers

This report highlights the importance of hydrophobic groups mimicking the side chains of aromatic amino acids, which are tryptophan, phenylalanine, and tyrosine, in guanidinium bearing poly(methacrylamide)s for the design of non-viral gene delivery agents. Guanidinium containing methacrylamide terpolymers are prepared by aqueous reversible addition-fragmentation chain transfer (aRAFT) polymerization with different hydrophobic monomers, N-(2-indolethyl)methacrylamide (IEMA), N-phenethylmethacrylamide (PhEMA), or N-(4-hydroxyphenethyl)methacrylamide (PhOHEMA) by aiming similar contents. The well-defined polymers are obtained with a molar mass of ≈15 000 g mol^-1 and ≈1.1 dispersity. All terpolymers demonstrate almost comparable in vitro cell viability and hemocompatibility profiles independent of the type of side chain. Although they all form positively charged, enzymatically stable polyplexes with plasmid DNA smaller than 200 nm, the incorporation of the IEMA monomer improve these parameters by demonstrating a higher DNA binding affinity and forming nanoassemblies of about 100 nm. These physicochemical characteristics are correlated with increased transfection rates in CHO-K1 cells dependent on the type of the monomer and the nitrogen to phosphate (N/P) ratio of the polyplexes, as determined by luciferase reporter gene assays.