In-situ biophysical characterization of high-concentration protein formulations using wNMR

High-concentration protein formulation is of paramount importance in patient-centric drug product development, but it also presents challenges due to the potential for enhanced aggregation and increased viscosity. The analysis of critical quality attributes often necessitates the transfer of samples from their primary containers together with sample dilution. Therefore, there is a demand for noninvasive, in situ biophysical methods to assess protein drug products directly in primary sterile containers, such as prefilled syringes, without dilution. In this study, we introduce a novel application of water proton nuclear magnetic resonance (wNMR) to evaluate the aggregation propensity of a high-concentration drug product, Dupixent® (dupilumab), under stress conditions. wNMR results demonstrate a concentration-dependent, reversible association of dupilumab in the commercial formulation, as well as irreversible aggregation when exposed to accelerated thermal stress, but gradually reversible aggregation when exposed to freeze and thaw cycles. Importantly, these results show a strong correlation with data obtained from established biophysical analytical tools widely used in the pharmaceutical industry. The application of wNMR represents a promising approach for in situ noninvasive analysis of high-concentration protein formulations directly in their primary containers, providing valuable insights for drug development and quality assessment.

The generation of genuine quadripartite Einstein-Podolsky-Rosen steering in an optical superlattice

Einstein-Podolsky-Rosen (EPR) steering is a quantum effect based on quantum entanglement and it is the key resource for building quantum networks because of its useful properties. Based on the criterion for genuine multipartite EPR steering, the genuine quadripartite EPR steering is confirmed and it can be generated by a spontaneous parametric down-conversion cascaded process with two sum-frequency generations in an optical superlattice. This occurs either below the oscillation threshold and without oscillation threshold. The influence of the parameters of cascaded nonlinear process on the quadripartite EPR steering among signal, idler, and two sum-frequency beams are also discussed. Choosing appropriate nonlinear parameters can achieve good quadripartite quantum steering. This scheme of the generation of genuine quadripartite EPR steering has potential applications in quantum communication and computing.

[Comparison of 5-year follow-up outcomes between"one-stop"procedure and long-term oral anticoagulants after radiofrequency catheter ablation in patients with atrial fibrillation]

Objective: To compare the 5-year follow-up outcomes of radiofrequency catheter ablation (RFCA) combined with left atrial appendage closure (LAAC) and long-term oral anticoagulant (OAC) after RFCA in patients with atrial fibrillation. Methods: This retrospective cross-sectional study included patients with atrial fibrillation who underwent"one-stop"procedure in the First Affiliated Hospital of Ningbo University from September 2015 to December 2017 (RFCA+LAAC group). Baseline data of patients were collected. Propensity score matching at the ratio of 1∶1 was used to select patients with atrial fibrillation who took long-term OAC after RFCA (RFCA+OAC group). The maintenance rate of sinus rhythm and the incidence of adverse events during follow-up were compared between the two groups. Results: A total of 110 patients were enrolled in the RFCA+LAAC group and RFCA+OAC group, respectively. Age of patients was (67.4±8.8) years in RFCA+LAAC group, and there were 42 (38.2%) female patients. Age of patients was (67.3±7.9) years in RFCA+OAC group, and there were 47 (42.7%) female patients. The patients were followed up for mean of (5.3±1.1) years. There was no significant difference in the maintenance rate of sinus rhythm (log-rank: χ2=0.277, P=0.602) and incidence of ischemic stroke events (2.7% (3/110) vs. 4.5% (5/110), P=0.719) during follow-up between the two groups. The incidence of bleeding events (6.4% (7/110) vs. 18.2% (20/110), P=0.008) and major bleeding events (1.8% (2/110) vs. 8.2% (9/110), P=0.030) was significantly higher in the RFCA+OAC group than in the RFCA+LAAC group. Conclusion: There is no significant difference between RFCA+LAAC group and RFCA+OAC group in maintenance rate of sinus rhythm and incidence of ischemic stroke events. Patients in the RFCA+LAAC group have a lower risk of bleeding events compared to the RFCA+OAC group.

Sedimentation behavior of quality and freeze-damaged aluminum-adjuvanted vaccines by wNMR

Vaccine sedimentation and resuspension are properties that vaccine makers use to characterize a suspension product during research and development as well as throughout the shelf life of the vaccine. Three vaccines with three different aluminum adjuvants and different antigens were selected and monitored over the course of sedimentation using water proton nuclear magnetic resonance (wNMR) relaxometry. This simple method measured fully intact, single-dose vaccine vials and reported sedimentation profiles for each, which readily distinguished freeze-stressed vaccines from unstressed vaccines.

Analysis of the Adsorbed Vaccine Formulations Using Water Proton Nuclear Magnetic Resonance-Comparison with Optical Analytics

PURPOSE

To evaluate wNMR, an emerging noninvasive analytical technology, for characterizing aluminum-adjuvanted vaccine formulations.

METHODS

wNMR stands for water proton nuclear magnetic resonance. In this work, wNMR and optical techniques (laser diffraction and laser scattering) were used to characterize vaccine formulations containing different antigen loads adsorbed onto AlPO4 adjuvant microparticles, including the fully dispersed state and the sedimentation process. All wNMR measurements were done noninvasively on sealed vials containing the adsorbed vaccine suspensions, while the optical techniques require transferring the adsorbed vaccine suspensions out of the original vial into specialized cuvette/tube for analysis. For analyzing fully dispersed suspensions, optical techniques also require sample dilution.

RESULTS

wNMR outperformed laser diffraction in differentiating high- and low-dose formulations of the same vaccine, while wNMR and laser scattering achieved comparable results on vaccine sedimentation kinetics and the compactness of fully settled vaccines.

CONCLUSION

wNMR could be used to analyze aluminum-adjuvanted formulations and to differentiate between formulations containing different antigen loads adsorbed onto aluminum adjuvant microparticles. The results demonstrate the capability of wNMR to characterize antigen-adjuvant complexes and to noninvasively inspect finished vaccine products.

Supramolecular Protein-Polyelectrolyte Assembly at Near Physiological Conditions-Water Proton NMR, ITC, and DLS Study

The in vivo potency of polyphosphazene immunoadjuvants is inherently linked to the ability of these ionic macromolecules to assemble with antigenic proteins in aqueous solutions and form physiologically stable supramolecular complexes. Therefore, in-depth knowledge of interactions in this biologically relevant system is a prerequisite for a better understanding of mechanism of immunoadjuvant activity. Present study explores a self-assembly of polyphosphazene immunoadjuvant-PCPP and a model antigen-lysozyme in a physiologically relevant environment-saline solution and neutral pH. Three analytical techniques were employed to characterize reaction thermodynamics, water-solute structural organization, and supramolecular dimensions: isothermal titration calorimetry (ITC), water proton nuclear magnetic resonance (wNMR), and dynamic light scattering (DLS). The formation of lysozyme-PCPP complexes at near physiological conditions was detected by all methods and the avidity was modulated by a physical state and dimensions of the assemblies. Thermodynamic analysis revealed the dissociation constant in micromolar range and the dominance of enthalpy factor in interactions, which is in line with previously suggested model of protein charge anisotropy and small persistence length of the polymer favoring the formation of high affinity complexes. The paper reports advantageous use of wNMR method for studying protein-polymer interactions, especially for low protein-load complexes.

[Feasibility and safety of closing large left atrial appendage using the LAmbre device]

Objective: To evaluate the feasibility and safety of the LAmbre occluder for large-diameter left atrial appendage occlusion. Methods: This study was a retrospective cohort study. Patients with large orifice of the left atrial appendage (≥31 mm) and occlusion with the LAmbre device in the Arrhythmia Center of Ningbo First Hospital were included from June 2018 to March 2020. Baseline data were collected and major perioperative complications of left atrial appendage occlusion (including death, stroke, instrumental embolism, cardiac tamponade, and major bleeding events) were recorded. Patients were followed up 45 days, 6 months and 12 months after surgery. The shunt and device-related thrombosis were recorded by esophageal cardiac ultrasound or pulmonary vein CT, and the occurrence of postoperative thromboembolism, bleeding events, death and other serious adverse events were recorded. Results: The average age and left atrial appendage ostial dimension of 32 patients (37.5% women) included in this research were (70.4±8.4) years old and (34.4±2.9) mm. The LAmbre device was successfully implanted in 31(96.9%) patients. No major complications occurred during the perioperative period. During the 12-month follow-up, pericardial tamponade occurred in 1(3.2%) patient and was recovered after treatment. There was no occluder edge shunt>5 mm in patients followed up by esophageal echocardiography. No significant peri-device leak, device-related thrombus, thromboembolism or death event has occurred. Conclusion: The LAmbre occluder may be feasible and safe for large-diameter left atrial appendage occlusion.

Genuine tripartite Einstein-Podolsky-Rosen steering in the cascaded nonlinear processes of third-harmonic generation

Recently, Einstein-Podolski-Rosen (EPR) steering has important application in quantum information processing, and it has been received considerable attention because of its uniqueness. The properties of quantum steering among three output fields generated by cascaded nonlinear processes of quasi-phase-matching third-harmonic generation in an optical cavity are investigated. Based on the criteria for multipartite EPR steering which proposed by He and Reid [PRL, 111, 250403 (2013)], the genuine tripartite EPR steering among pump, second-harmonic, and third-harmonic is demonstrated. The parameters which affect the quantum property are also discussed.

Correction to: Nondestructive Quantitative Inspection of Drug Products Using Benchtop NMR Relaxometry-the Case of NovoMix® 30

Typesetting error occurred and author corrections to the equations and text edits at the proofing stage were not incorporated in the published article. The original article has been corrected.

Nondestructive Quantitative Inspection of Drug Products Using Benchtop NMR Relaxometry-the Case of NovoMix® 30

Batch-level inference-based quality control is the standard practice for drug products. However, rare drug product defects may be missed by batch-level statistical sampling, where a subset of vials in a batch is tested quantitatively but destructively. In 2013, a suspension insulin product, NovoLog® Mix 70/30 was recalled due to a manufacturing error, which resulted in insulin strength deviations up to 50% from the labeled value. This study analyzed currently marketed FlexPen® devices by the water proton transverse relaxation rate using a benchtop nuclear magnetic resonance relaxometer. The water proton transverse relaxation rate was found to be sensitive to detecting concentration changes of the FlexPen® product. These findings support the development of vial-level verification-based quality control for drug products where every vial in a batch is inspected quantitatively but nondestructively.

[Predictive value of typical cataplexy+ DQB1*0602 positive to hypocretin-1 reduction in cerebrospinal fluid in patients with narcolepsy]

Objective: To discusses the predictive value of typical cataplexy+ HLA-DQB1*0602 positive to hypocretin-1 (HCRT-1) reduction in cerebrospinal fluid (CSF) in patients with narcolepsy. Methods: A total of 165 narcoleptic patients, who were diagnosed at the Sleep Center of Peking University People's Hospital and Peking University International Hospital from March 2003 to March 2017, were recruited. The CSF HCRT-1 level and DQB1*0602 were measured in all the subjects. The narcoleptic patients were divided into two groups: typical cataplexy+ DQB1*0602 positive were CH group, and others who were not typical cataplexy and DQB1*0602 positive simultaneously were NCH group. The HCRT-1 level in CSF was declared to have a serious reduction when HCRT-1≤110 ng/L. According to this standard, the CH group and NCH group were subdivided into sub-groups and the data was analyzed to investigate the predictive value of typical cataplexy+ HLA-DQB1*0602 positive to HCRT-1 reduction. Results: There were 142 patients in CH group, including 137 patients with HCRT-1 reduction and 5 patients without. There were 23 patients in NCH group, including 15 patients with HCRT-1 reduction and 8 patients without. The positive predictive value of typical cataplexy+ DQB1*0602 positive for the reduction of HCRT-1 in CSF was 96.5%. Typical cataplexy+ DQB1*0602 positive had a good consistency with the HCRT-1 reduction in CSF (χ(2)=26.7, P<0.001). Conclusion: Typical cataplexy+ DQB1*0602 positive has a good predictive value to the HCRT-1 reduction in CSF in patients with narcolepsy.

Water proton NMR detection of amide hydrolysis and diglycine dimerization

The transverse relaxation rate of water protons R2(1H2O) is found to be sensitive to amide hydrolysis and diglycine dimerization. The results demonstrate the feasibility of using R2(1H2O) as a diagnostic tool to detect chemical changes in aqueous solutions. Potential applications include drug product formulation and inspection.

[The study on the inhibitive effects of recombinant parathyroid hormone (1-34) on osteolysis in a murine calvarial model induced by wear particles]

Objective: To investigate the effect of different doses of recombinant parathyroid hormone (PTH) (1-34) on osteolysis in a murine calvarial model. Methods: In total, 48 adult male C57BL/J6 mice were randomly divided into four groups: the sham group, the vehicle group, the low dose-, and high dose PTH group (n=12 each group). Mice in the PTH groups were treated with local injection of recombinant PTH at 30 or 60 μg·kg^-1·d^-1, intermittent injection 3 times per week for two weeks. Mice in the sham and vehicle groups received local injection of saline daily. Two weeks after surgery, calvarial tissue and peripheral blood were harvested for further analysis. Osteolysis was assessed by micro-computed tomography. The mRNA and protein expression of osteoprotegerin (OPG) and receptor activator for nuclear factor-κB Ligand (RANKL) of calvarial tissue and peripheral blood were tested by real-time PCR and ELISA, respectively. Results: Compared with the vehicle group, PTH treatment significantly inhibited the severity of osteolysis and improved the bone volume. Real time-PCR and ELISA showed that PTH significantly increased the mRNA and protein expression of OPG and reduced the RANKL/OPG ratio. Conclusion: These findings suggest that local application of PTH could effectively inhibit wear-particle-induced-osteolysis in a murine calvarial model.

Linear dependence of the water proton transverse relaxation rate on the shear modulus of hydrogels

It is found that hydrogelation of peptides enhances the transverse relaxation rate R2 of water protons but has no effect on the longitudinal relaxation rate R1 and the diffusion coefficient D. The magnitude of water proton R2 enhancement increases linearly with the shear modulus G of hydrogels.

Correction: Conformational transition of a non-associative fluorinated amphiphile in aqueous solution

Correction for ‘Conformational transition of a non-associative fluorinated amphiphile in aqueous solution’ by Marc B. Taraban et al., RSC Adv., 2014, 4, 54565–54575.

Conformational transition of a non-associative fluorinated amphiphile in aqueous solution

A non-associative fluorinated amphiphile was synthesized. Instead of self-association at high concentrations, this amphiphile undergoes conformational transition in which the hydrophilic tails wrap around the fluorocarbon core to shield it from water, bearing certain similarity to protein folding in a crowded environment.

Using Small-Angle Scattering Techniques to Understand Mechanical Properties of Biopolymer-Based Biomaterials

The design and engineering of innovative biopolymer-based biomaterials for a variety of biomedical applications should be based on the understanding of the relationship between their nanoscale structure and mechanical properties. Down the road, such understanding could be fundamental to tune the properties of engineered tissues, extracellular matrices for cell delivery and proliferation/differentiation, etc. In this tutorial review, we attempt to show in what way biomaterial structural data can help to understand the bulk material properties. We begin with some background on common types of biopolymers used in biomaterials research, discuss some typical mechanical testing techniques and then review how others in the field of biomaterials have utilized small-angle scattering for material characterization. Detailed examples are then used to show the full range of possible characterization techniques available for biopolymer-based biomaterials. Future developments in the area of material characterization by small-angle scattering will undoubtedly facilitate the use of structural data to control the kinetics of assembly and final properties of prospective biomaterials.

Split of chiral degeneracy in mechanical and structural properties of oligopeptide-polysaccharide biomaterials

Enantiomeric biomaterials which are mirror images of each other are characterized by chiral degeneracy--identical structural characteristics and bulk material properties. The addition of another chiral component, D-polysaccharide, has been shown to split such degeneracy and result in two distinct biomaterials. Dynamic oscillatory rheometry and small-angle X-ray scattering demonstrate that the natural biochirality combination of L-peptides and D-polysaccharides assembles faster, has higher elastic moduli (G'), and is structurally more beneficial as opposed to the alternative D-peptide and D-polysaccharide combination. Chemical modifications of the OH-groups in α-D-glucose units in D-polysaccharides weaken such splitting of chiral degeneracy. These findings form a basis to design novel biomaterials and provide additional insight on why proteins and polysaccharides have oppoiste chirality in the biological world.

An interplay between electrostatic and polar interactions in peptide hydrogels

Inherent chemical programmability available in peptide-based hydrogels has allowed diversity in the development of these materials for use in biomedical applications. Within the 20 natural amino acids, a range of chemical moieties are present. Here we used a mixing-induced self-assembly of two oppositely charged peptide modules to form a peptide-based hydrogel. To investigate electrostatic and polar interactions in the hydrogel, we replace amino acids from the negatively charged acidic glutamic acid (E) to the uncharged polar glutamine (Q) on a negatively charged peptide module, while leaving the positively charged module unchanged. Using dynamic rheology, the mechanical properties of each hydrogel were investigated. It was found that the number, but not the location, of electrostatic interactions (E residues) dictate the elastic modulus (G') of the hydrogel, compared to polar interactions (Q residues). Increased electrostatic interactions also promote faster peptide assembly into the hydrogel matrix, and result in the decrease of T2 relaxation times of H2 O and trifluoroacetic acid. Small-angle X-ray scattering (SAXS) showed that changing from electrostatic to polar interactions affects the ability to form fibrous networks: from the formation of elongated fibers to no fiber assembly. This study reveals the systematic effects that the incorporation of electrostatic and polar interactions have when programmed into peptide-based hydrogel systems. These effects could be used to design peptide-based biomaterials with predetermined properties.

Enhancing biocompatibility of D-oligopeptide hydrogels by negative charges

Oligopeptide hydrogels are emerging as useful matrices for cell culture with commercial products on the market, but L-oligopeptides are labile to proteases. An obvious solution is to create D-oligopeptide hydrogels, which lack enzymatic recognition. However, D-oligopeptide matrices do not support cell growth as well as L-oligopeptide matrices. In addition to chiral interactions, many cellular activities are strongly governed by charge-charge interactions. In this work, the effects of chirality and charge on human mesenchymal stem cell (hMSC) behavior were studied using hydrogels assembled from oppositely charged oligopeptides. It was found that negative charges significantly improved hMSC viability and proliferation in D-oligopeptide gels but had little effect on their interactions with L-oligopeptide gels. This result points to the possibility of using charge and other factors to engineer biomaterials whose chirality is distinct from that of natural biomaterials, but whose performance is close to that of natural biomaterials.

BCLAF1 is a radiation-induced H2AX-interacting partner involved in γH2AX-mediated regulation of apoptosis and DNA repair

H2AX, a histone H2A variant, has a key role in the cellular response to DNA double-strand breaks (DSBs). H2AX senses DSBs through rapid serine 139 phosphorylation, concurrently leading to the formation of phospho-(γ)H2AX foci with various proteins. However, in the cells with different sensitivity to ionizing radiation (IR)-induced DSBs, still incomplete are those specific proteins selectively recruited by γH2AX to decide different cell fates. Because the abundance of γH2AX indicates the extent of DSBs, we first identified IR-induced dose-dependent H2AX-interacting partners and found that Bcl-2-associated transcription factor 1 (BCLAF1/Btf) showed enhanced association with γH2AX only under high-dose radiation. In acutely irradiated cells, BCLAF1 promoted apoptosis of irreparable cells through disturbing p21-mediated inhibition of Caspase/cyclin E-dependent, mitochondrial-mediated pathways. Meanwhile, BCLAF1 co-localized with γH2AX foci in nuclei and stabilized the Ku70/DNA-PKcs complex therein, facilitating non-homologous end joining (NHEJ)-based DSB repair in surviving cells. In tumor cells, BCLAF1 was intrinsically suppressed, leading to formation of anti-apoptotic Ku70-Bax complexes and disruption of Ku70/DNA-PKcs complexes, all of which contribute to tumor-associated apoptotic resistance and cell survival with defective NHEJ DNA repair. For the first time, our studies reveal that, based on the extent of DNA damage, BCLAF1 is involved in the γH2AX-mediated regulation of apoptosis and DNA repair, and is a γH2AX-interacting tumor suppressor.

Chirality-Mediated Mechanical and Structural Properties of Oligopeptide Hydrogels

The origin and the effects of homochirality in the biological world continuously stimulate numerous hypotheses and much debate. This work attempts to look at the biohomochirality issue from a different angle-the mechanical properties of the bulk biomaterial and their relation to nanoscale structures. Using a pair of oppositely charged peptides that co-assemble into hydrogels, we systematically investigated the effect of chirality on the mechanical properties of these hydrogels through different combinations of syndiotactic and isotactic peptides. It was found that homochirality confers mechanical advantage, resulting in higher elastic modulus and strain yield value. Yet, heterochirality confer kinetic advantage, resulting in faster gelation. Structurally, both homochiral and heterochiral hydrogels are made of fibers interconnected by lappet-like webs, but the homochiral peptide fibers are thicker and denser. The result highlights the possible role of biohomochirality in the evolution and/or natural selection of biomaterials.

Viscoelastic properties and nanoscale structures of composite oligopeptide-polysaccharide hydrogels

Biocompatible and biodegradable peptide hydrogels are drawing increasing attention as prospective materials for human soft tissue repair and replacement. To improve the rather unfavorable mechanical properties of our pure peptide hydrogels, in this work we examined the possibility of creating a double hydrogel network. This network was created by means of the coassembly of mutually attractive, but self-repulsive oligopeptides within an already-existing fibrous network formed by the charged, biocompatible polysaccharides chitosan, alginate, and chondroitin. Using dynamic oscillatory rheology experiments, it was found that the coassembly of the peptides within the existing polysaccharide network resulted in a less stiff material as compared to the pure peptide networks (the elastic modulus G' decreased from 90 to 10 kPa). However, these composite oligopeptide-polysaccharide hydrogels were characterized by a greater resistance to deformation (the yield strain γ grew from 4 to 100%). Small-angle neutron scattering (SANS) was used to study the 2D cross-sectional shapes of the fibers, their dimensional characteristics, and the mesh sizes of the fibrous networks. Differences in material structures found with SANS experiments confirmed rheology data, showing that incorporation of the peptides dramatically changed the morphology of the polysaccharide network. The resulting fibers were structurally very similar to those forming the pure peptide networks, but formed less stiff gels because of their markedly greater mesh sizes. Together, these findings suggest an approach for the development of highly deformation-resistant biomaterials.

The Effect of Ionic Strength on the Mechanical, Structural and Transport Properties of Peptide Hydrogels

It is found that the elastic modulus of a peptide hydrogel increases linearly with the logarithm of its ionic strength. This result indicates that the elastic modulus of this class of hydrogels can be tuned by the ionic strength in a highly predictable manner. Small-angle X-ray scattering studies reveal that higher ionic strength leads to thinner but more rigid peptide fibers that are packed more densely. The self-diffusion coefficient of small molecules inside the hydrogel decrease linearly with its ionic strength, but this decrease is mainly a salt effect rather than diffusion barriers imposed by the hydrogel matrix.

Mutually reinforced multicomponent polysaccharide networks

Networks made from chitosan and alginate have been utilized as prospective tissue engineering scaffolds due to material biocompatibility and degradability. Calcium (Ca(2+) ) is often added to these networks as a modifier for mechanical strength enhancement. In this work, we examined changes in the bulk material properties of different concentrations of chitosan/alginate mixtures (2, 3, or 5% w/w) upon adding another modifier, chondroitin. We further examined how material properties depend on the order the modifiers, Ca(2+) and chondroitin, were added. It was found that the addition of chondroitin significantly increased the mechanical strength of chitosan/alginate networks. Highest elastic moduli were obtained from samples made with mass fractions of 5% chitosan and alginate, modified by chondroitin first and then Ca(2+) . The elastic moduli in dry and hydrated states were (4.41 ± 0.52) MPa and (0.11 ± 0.01) MPa, respectively. Network porosity and density were slightly dependent on total polysaccharide concentration. Average pore size was slightly larger in samples modified by Ca(2+) first and then chondroitin and in samples made with 3% starting mass fractions. Here, small-angle neutron scattering (SANS) was utilized to examine mesh size of the fibrous networks, mass-fractal parameters and average dimensions of the fiber cross-sections prior to freeze-drying. These studies revealed that addition of Ca(2+) and chondroitin modifiers increased fiber compactness and thickness, respectively. Together these findings are consistent with improved network mechanical properties of the freeze-dried materials.

Diffusion of small molecules inside a peptide hydrogel

A set of four phenylalanine analogues experiences diffusion retardation when transferred from phosphate-buffered saline into a peptide hydrogel of the same pH and ionic strength. The extent of retardation increases linearly with logP(oct), their lipophilicity.

Directly produced three-color entanglement by quasi-phase-matched third-harmonic generation

A new scheme is presented to directly produce fundamental, second-, and third-harmonic three-color continuous-variable (CV) entangled beams by cascaded quasi-phase-matched third-harmonic generation (THG) in an optical cavity. THG can be achieved with high efficiency through a coupled sum-frequency process between the second-harmonic and the fundamental fields. It is demonstrated that the three beams (fundamental, second-, and third-harmonic fields) are entangled with each other according to the CV entanglement criterion. In this scheme, only one crystal and one pump field can generate three-color CV entangled beams separated by an octave in frequency through quasi-phase-matched cascaded nonlinear process, which may be very useful for the applications in quantum communication and computation networks.

Linear Dependency of NMR Relaxation Rates on Shear Modulus in Hydrogels

It is found that the NMR relaxation rates of diffusants in peptide hydrogels have a linear dependency on the shear modulus of the hydrogels. This finding opens the door for non-invasive and forceless mechanical characterizations of materials and tissues using NMR and MRI.

Separation of Fluorinated Amino Acids and Oligopeptides from their Non-fluorinated Counterparts using High-performance Liquid Chromatography

Chromatographic conditions for the separation of fluorinated amino acids and oligopeptides from their non-fluorinated counterparts were explored. The separation of six pairs of analytes, including both aromatic and aliphatic fluorocarbons, was investigated at various temperatures using both hydrocarbon and fluorocarbon columns and eluents. Our results show that when hydrocarbon eluents are used, fluorocarbon column provides better separation of fluorinated amino acids or oligopeptides from their non-fluorinated counterparts; when fluorocarbon eluents are used, hydrocarbon column provides better separation of fluorinated amino acids or oligopeptides from their non-fluorinated counterparts. These chromatographic behaviors reflect the fluorophilicity possessed by fluorinated amino acids and oligopeptides.

Delivered dose: a drug-centric phenotype for chemotherapy dose individualization

It is pointed out that genotype-based approaches are unlikely to be effective at dose individualization. Delivered dose, which refers to the amount of drug delivered to the point of action to be measured by quantitative imaging techniques, is a drug-centric phenotype that separates pharmacokinetic effects from pharmacodynamic effects. Delivered dose serves as a midway measurable numeric parameter between drug administration and therapy outcome. One potential way to reduce chemotherapy outcome variation is to individualize prescribed drug so that uniform delivered dose is achieved across the patient population.

The effect of a side chain-backbone swap on protein stability

To assess the relative importance of backbone hydrogen bonding (H-bonding) vs. side chain hydrophobicity in protein structural formation, a method called side chain-backbone swap is proposed. Such a method swaps the side chain and backbone portions of certain amino acid residues, such as Asp, Glu, Asn, Gln, Lys, and Arg. Such a swap retains the sequence of a polypeptide and preserves the identity of the backbone linkage. On the other hand, the swap disrupts backbone H-bonding geometry because of the introduction of extra methylene groups into the peptide backbone. In this project, we chose the two-stranded alpha-helical coiled-coil to implement side chain-backbone swap. A pair of 36-residue peptides was designed. The two peptides have identical sequence with four residues in each heptad repeat occupied by glutamyl residues. Each glutamic acid was incorporated either as alpha-glutamyl residue (the peptide is denoted as alpha-Glu-36) or as gamma-glutamyl residue (the peptide is denoted as gamma-Glu-36). The inter-conversion between the two peptides constitutes a side chain-backbone swap. Residues constituting the hydrophobic core of the coiled-coil, however, are left unchanged. The peptide pair was characterized by circular dichroism spectroscopy, reversed-phase liquid chromatography (RPLC), and two-dimensional nuclear magnetic resonance (NMR). The results indicate that alpha-Glu-36 is a two-stranded alpha-helical coiled-coil while gamma-Glu-36 lacks stable structural elements. It is concluded that, at least for coiled-coils where hydrophobic interactions are predominantly long-range, local backbone H-bonding is a required for structural formation, consistent with a hierarchic folding mechanism. The methodological implication of side chain-backbone swap is also discussed.

Fluorocarbon nanoparticles as multifunctional drug delivery vehicles

The history and current status of fluorocarbon nanoparticles in biomedicine is briefly reviewed. The deficiencies of current fluorocarbon nanoparticle formulations are highlighted. Strategies to remedy such deficiencies and to functionalize fluorocarbon nanoparticles are presented. Potential applications of fluorocarbon nanoparticles as multifunctional drug delivery vehicles are discussed. The strength of fluorocarbon nanoparticles as drug delivery vehicles is that they integrate drug delivery with non-invasive MR imaging so that the biodistribution of the pharmaceutical entity (drug + delivery vehicle) can be monitored in real time. This, in turn, permits the physician to adjust treatment plan for each patient based on his/her actual response to the ongoing treatment.

The Design and Synthesis of Highly Branched and Spherically Symmetric Fluorinated Macrocyclic Chelators

Two novel, highly fluorinated macrocyclic chelators with highly branched and spherically symmetric fluorocarbon moieties have been designed and efficiently synthesized. This is achieved by conjugating a spherically symmetric fluorocarbon moiety to the macrocyclic chelator DOTA, with or without a flexible oligo-oxyethylene linker between these two parts. As a result of the spherical symmetry, all 27 fluorine atoms in each fluorinated chelator give a sharp singlet (19)F NMR signal. The hydrophilicity and the (19)F relaxation behavior of fluorinated chelators can be modulated by the insertion of a flexible linker between the fluorocarbon moiety and the macrocyclic linker. These chelators serve as prototypes for (1)H-(19)F dual-nuclei magnetic resonance imaging agents.

The Design and Synthesis of Highly Branched and Spherically Symmetric Fluorinated Oils and Amphiles

A new emulsifier design principle, based on concepts borrowed from protein science, is proposed. Using this principle, a class of highly branched and spherically symmetric fluorinated oils and amphiles has been designed and synthesized, for potential applications in the construction of fluorocarbon nanoparticles. The Mitsunobu reaction was employed as the key step for introducing three perfluoro-tert-butoxyl groups into pentaerythritol derivatives with excellent yields and extremely simple isolation procedures. Due to the symmetric arrangement of the fluorine atoms, each fluorinated oil or amphile molecule gives one sharp singlet (19)F NMR signal.

The synthesis of a geminally perfluoro-tert-butylated beta-amino acid and its protected forms as a potential pharmacokinetic modulator and reporter for peptide-based pharmaceuticals

To modulate and report the pharmacokinetics of peptide-based pharmaceuticals, a novel geminally perfluoro-tert-butylated beta-amino acid (betaFa) and its Fmoc- and Boc-protected forms were designed and synthesized. betaFa was incorporated into a model tripeptide via standard solid-phase chemistry. Both the amino acid (free and protected) and the tripeptide show a sharp singlet 19F NMR signal. Reversed-phase chromatography and 1-octanol/water partition measurements demonstrate that betaFa is extremely hydrophobic.

Enantioselective synthesis of (2R, 3S)- and (2S, 3R)-4,4,4-trifluoro-N-Fmoc-O-tert-butyl-threonine and their racemization-free incorporation into oligopeptides via solid-phase synthesis

An efficient method for the enantioselective synthesis of (2R, 3S)- and (2S, 3R)-4,4,4-trifluoro-N-Fmoc-O-tert-butyl-threonine on multigram scales was developed. Absolute configurations of the two stereoisomers were ascertained by X-ray crystallography. Racemization-free coupling conditions for the incorporation of tfT into oligopeptides were then explored. For solution-phase synthesis, tfT racemization was not an issue under conventional coupling conditions. For solid-phase synthesis, the following conditions were identified to achieve racemization-free synthesis: if tfT (3.0 equiv) was not the first amino acid to be linked to the resin (1.0 equiv), the condition is 2.7 equiv DIC/3.0 equiv HOBt as the coupling reagent at 0 degrees C for 20 h; if tfT (3.0 equiv) was the first amino acid to be linked to the resin (1.0 equiv), then 1.0 equiv of CuCl(2) needs to be added to the coupling reagent.

Strategy for olive mill wastewater treatment and reuse with a sewage plant in an arid region

This study was conducted to evaluate the treatability of OMW (olive mill wastewater) with sewage and sewage sludge, which could supplement nutrients and microbes required for OMW treatment and reduce its possible toxicity. The amount of OMW added to an aeration tank was based on the loading difference between the designed and actual COD loads, while the amount added to anaerobic digestion for energy recovery was determined by CH4 production. The COD removal efficiencies were 70-85% for both systems. Compost of OMW with dried sewage sludge also showed a similar temperature profile without OMW addition. This strongly suggested that OMW can be treated at a sewage plant without pretreatment and the treated effluent can be reused in irrigation for an arid region.

Repeated rapid shear-responsiveness of peptide hydrogels with tunable shear modulus

A pair of mutually attractive but self-repulsive decapeptides, with alternating charged/neutral amino acid sequence patterns, was found to co-assemble into a viscoelastic material upon mixing at a low total peptide concentration of 0.25 wt %. Circular dichroism spectroscopy of individual decapeptide solutions revealed their random coil conformation. Transmission electron microscopy images showed the nanofibrillar network structure of the hydrogel. Dynamic rheological characterization revealed its high elasticity and shear-thinning nature. Furthermore, the co-assembled hydrogel was capable of rapid recoveries from repeated shear-induced breakdowns, a property desirable for designing injectable biomaterials for controlled drug delivery and tissue engineering applications. A systematic variation of the neutral amino acids in the sequence revealed some of the design principles for this class of biomaterials. First, viscoelastic properties of the hydrogels can be tuned through adjusting the hydrophobicity of the neutral amino acids. Second, the beta-sheet propensity of the neutral amino acid residue in the peptides is critical for hydrogelation.

Algorithmic Generation of Freely Jointed Hard Sphere Chains and Properties of Inertial Tensors

A statistical algorithm, capable of generating a large number of freely jointed hard sphere chains, is presented. This is the first of a series of algorithms being developed to model unfolded proteins by different modes of hard sphere chains. The aim of these studies is to systematically investigate the effects of different factors, such as atomic radii, bond angles, torsion angles, chain length, etc., on the conformation of unfolded proteins and other random polymers. As continuous models, various types of hard sphere chains enable one to isolate the aforementioned factors one at a time for investigation and thus are advantageous over discrete lattice models. In particular, the freely jointed hard sphere chain model allows one to evaluate the excluded volume effect. As a first step in this endeavor, the average determinant D(N, r) and the average trace T(N, r) of the inertial tensor A of the random chains were calculated at various sphere radii r and chain lengths N. It is found that both the average determinant D(N, r) and the average trace T(N, r) scale linearly with chain length N after logarithmic transformation. However, the critical exponent of D(N, r) increases with r faster than that of T(N, r) as a result of the non-commutativity between the det operator and the average operator < >. The significance of the algorithm and the results obtained on understanding random polypeptide chains are discussed.

Coiled-coils: stability, specificity, and drug delivery potential

The coiled-coil is a ubiquitous protein folding and assembly motif made of alpha-helices wrapping around each other forming a supercoil. The sequences of coiled-coils are made of seven-residue repeats, called heptads, and thus are polymer-like. Due to its simplicity and regularity, the coiled-coil is the most extensively studied protein motif. In this review, results on coiled-coil stability and specificity from structural and biophysical studies are summarized. It is pointed out that the primary sequences of coiled-coils over specify the secondary structure but under specify the tertiary/quaternary structure. This leads to two unique features of coiled-coil structure: linkage between stability and specificity and decoupling of secondary and tertiary/quaternary structural specificity. This is followed by a discussion of the potential of coiled-coils as drug delivery vehicles, particularly the prospect in two-staged pretargeted delivery. Such potentials are intimately related to the unique structural features of coiled-coils. The aim of this review is to illustrate how knowledge on protein stability and specificity can be used in the de novo design of peptide-based drug delivery vehicles with well-defined structure and interaction features.

Standard state and thermodynamic self-consistency

It is pointed out that even though the standard state for solutions is a fictitious state, it nonetheless should be thermodynamically self-consistent. Using a volumetric constraint, it is shown that the biochemical standard state concentration of 1M is too high for macromolecules like proteins and nucleic acids that it violates volumetric self-consistency. Also, at 1 M standard state, the mole fraction of these macromolecular solutes is not the commonly held value of 1/55.5, but rather a meaningless negative number. Thus, the ideal mixing entropy (also called cratic entropy) cannot be meaningfully calculated for macromolecules at such a standard state. The relevance of this conclusion to the interpretation of standard bimolecular binding entropy is discussed.

Contribution of translational and rotational motions to molecular association in aqueous solution

Much uncertainty and controversy exist regarding the estimation of the enthalpy, entropy, and free energy of overall translational and rotational motions of solute molecules in aqueous solutions, quantities that are crucial to the understanding of molecular association/recognition processes and structure-based drug design. A critique of the literature on this topic is given that leads to a classification of the various views. The major stumbling block to experimentally determining the translational/rotational enthalpy and entropy is the elimination of vibrational perturbations from the measured effects. A solution to this problem, based on a combination of energy equi-partition and enthalpy-entropy compensation, is proposed and subjected to verification. This method is then applied to analyze experimental data on the dissociation/unfolding of dimeric proteins. For one translational/rotational unit at 1 M standard state in aqueous solution, the results for enthalpy (H degrees (tr)), entropy (S degrees (tr)), and free energy (G degrees (tr)) are H (degrees) (tr) = 4.5 +/- 1.5RT, S (degrees) (tr) = 5 +/- 4R, and G (degrees) (tr) = 0 +/- 5RT. Therefore, the overall translational and rotational motions make negligible contribution to binding affinity (free energy) in aqueous solutions at 1 M standard state.