An SPR-based method for Hill coefficient measurements: the case of insulin-degrading enzyme

Intrinsically photoluminescent hydrogels to measure peptides‑copper binding affinities

NH2 decorated intrinsically photoluminescent hydrogels (IPH-NH2) were functionalized with the addition of various peptides via EDC/NHS coupling method. These peptidic devices bind copper with binding affinities depending on surface functionalization. Particularly, fluorescence analysis of copper titrations, alongside the determination of quenching efficiency and lifetime measurements, allowed to assess binding constants and to elucidate the underlying binding mechanism. Various peptides, having the same copper binding amino acidic residues (GHK) but different chain lengths, were tested and it was found that increasing the distance of the GHK sequence from the IPH-NH2 surface resulted in a decrease in the binding constant, as well as a reduction in quenching efficiency, whereas the binding mechanism remained unchanged as indicated by lifetime measurements. This method not only provides binding constants for peptides immobilized on biosensor surfaces or pre-fabricated devices without altering their structure, but also contributes to the optimization of biosensor design, tailoring it to its intended application.

Penicillin-like mimotopes from autodisplayed Fv-antibody library inhibiting β-lactamase activity

A penicillin-like mimotope was screened from an Fv-antibody library which had the inhibition activity of β-lactamase. Fv-antibody indicated the variable region (VH) of the immunoglobulin G, which includes three complementarity determining regions (CDRs). The Fv-antibody library was then prepared by randomizing the complementarity determining region 3 (CDR3), and it was expressed on the outer membrane of E. coli. The penicillin-like mimotopes were screened from the Fv-antibody library using magnetic beads with an immobilized monoclonal anti-penicillin antibody. The screened mimotopes were expressed as soluble Fv-antibodies and were also synthesized into peptides (11-mer). The binding affinity (KD) of the expressed Fv-antibodies and synthesized peptides was estimated using SPR measurements. The β-lactamase inhibition activity of the Fv-antibodies and synthetic peptides was estimated using colorimetry based on the formation of penicilloic acid. The penicillin-like mimotopes of the expressed Fv-antibodies and synthesized peptides were demonstrated to have β-lactamase inhibition activity in the bacterial lysates. Finally, the docking analysis of β-lactamase and the screened CDR3 sequences demonstrated that the screened CDR3 sequences were specifically bound to the binding sites of β-lactamase.

Detection of insulin oligomeric forms by a novel surface plasmon resonance-diffusion coefficient based approach

Insulin is commonly used to treat diabetes and undergoes aggregation at the site of repeated injections in diabetic patients. Moreover, aggregation is also observed during its industrial production and transport and should be avoided to preserve its bioavailability to correctly adjust glucose levels in diabetic patients. However, monitoring the effect of various parameters (pH, protein concentration, metal ions, etc.) on the insulin aggregation and oligomerization state is very challenging. In this work, we have applied a novel Surface Plasmon Resonance (SPR)-based experimental approach to insulin solutions at various experimental conditions, monitoring how its diffusion coefficient is affected by pH and the presence of metal ions (copper and zinc) with unprecedented sensitivity, precision, and reproducibility. The reported SPR method, hereby applied to a protein for the first time, besides giving insight into the insulin oligomerization and aggregation phenomena, proved to be very robust for determining the diffusion coefficient of any biomolecule. A theoretical background is given together with the software description, specially designed to fit the experimental data. This new way of applying SPR represents an innovation in the bio-sensing field and expanding the potentiality of commonly used SPR instruments well over the canonical investigation of biomolecular interactions.

In Silico Investigation of the Clinical Translatability of Competitive Clearance Glucose-Responsive Insulins

The glucose-responsive insulin (GRI) MK-2640 from Merck was a pioneer in its class to enter the clinical stage, having demonstrated promising responsiveness in in vitro and preclinical studies via a novel competitive clearance mechanism (CCM). The smaller pharmacokinetic response in humans motivates the development of new predictive, computational tools that can improve the design of therapeutics such as GRIs. Herein, we develop and use a new computational model, IM3PACT, based on the intersection of human and animal model glucoregulatory systems, to investigate the clinical translatability of CCM GRIs based on existing preclinical and clinical data of MK-2640 and regular human insulin (RHI). Simulated multi-glycemic clamps not only validated the earlier hypothesis of insufficient glucose-responsive clearance capacity in humans but also uncovered an equally important mismatch between the in vivo competitiveness profile and the physiological glycemic range, which was not observed in animals. Removing the inter-species gap increases the glucose-dependent GRI clearance from 13.0% to beyond 20% for humans and up to 33.3% when both factors were corrected. The intrinsic clearance rate, potency, and distribution volume did not apparently compromise the translation. The analysis also confirms a responsive pharmacokinetics local to the liver. By scanning a large design space for CCM GRIs, we found that the mannose receptor physiology in humans remains limiting even for the most optimally designed candidate. Overall, we show that this computational approach is able to extract quantitative and mechanistic information of value from a posteriori analysis of preclinical and clinical data to assist future therapeutic discovery and development.