BioChem Defense Technology (BCDT) develops 5H-EAF—an erythritol-capped linear penta-histidine peptide (MW ≈ 868 Da; C₃₆H₄₉N₁₅O₁₁) whose five imidazoles (pKa ≈ 6.0–6.1) define Channel E at endosomal pH and Channel C at physiologic pH. Public materials describe non-confidential science from ChemRxiv v7, under dual-use stewardship.
Brand mark · BCDT
The gap
The gap is the acidified tumor endosome and macrophage window at pH 5.5–6.5, where histidine occupancy actually moves (Channel E). That is compartment chemistry, not a delivery construct and not an oncology protocol. Channel C remains the physiologic (~7.4) soft-metal window.
Channel E (His⁺, endosomal pH 5.5–6.5, net +4 to +5): competitive occupancy of acidic sites and local neutralization of negative endosomal-pore potential. The effect is electrostatic screening, not mechanical occlusion.
Channel C (His⁰, pH ~7.4): imidazole-N coordination that prefers Hg(II) and Pb(II); Zn(II) and Cu(I) remain weakly bound. The cycle is a reversible electrostatic switch, not a permanent steric block.
Does not inhibit furin. Does not insert into membranes. Does not carry a cytotoxic payload.
This public site presents only non-confidential science from the open v7 preprint: mechanism abstracts, computational methods summaries, and dual-use governance language. No controlled recipes, production protocols, or weaponization pathways.
Technology
High-level, non-confidential description of the published platform. Structural and computational detail lives in the ChemRxiv preprint (v7). Full computational packages remain under appropriate agreements.
Composition (public abstract)
01
Charge collapses as the five imidazoles deprotonate. Channel C is the soft-metal coordination window—preferential imidazole-N ligation of Hg(II) and Pb(II), with Zn(II) and Cu(I) remaining weakly bound.
02
Histidine protonation drives a net +4 to +5 charge. Channel E supports competitive occupancy of acidic sites and local neutralization of negative endosomal-pore potential—electrostatic screening, not mechanical occlusion.
03
Return to neutrality reverses binding for release and reagent recycling. The functional cycle is a single, reversible electrostatic switch rather than a permanent steric block.
At endosomal pH 5.5–6.5 the molecule protonates to a net charge of approximately +4 to +5 (Channel E dominant). At physiologic pH the charge collapses (Channel C dominant), enabling preferential coordination of soft heavy-metal ions. Return to neutrality reverses binding. This reversible electrostatic switch is the core of the published platform.
Channel E
pH 5.5 – 6.5
Channel C
pH ~7.4
pKa
≈ 6.0 – 6.1
Applications
Dual-use by nature: the same electrostatic / pH logic spans biodefense-relevant modeling, soft heavy-metal research, and acidified tumor / endosomal niches as compartment chemistry. Everything below is research framing, not product claims. The public educational companion cited in v7 Methods is MoleculoSphere 5D.
Computational evaluation of electrostatic engagement with furin-processed polycationic motifs and endosomal pore architectures — framed as protective research at the non-confidential abstract level.
Channel C coordination of Hg(II) / Pb(II) class cations as reported in the v7 preprint. Zn(II) and Cu(I) remain weakly bound — this is not a copper or zinc chelator claim.
Tumor endosomes and macrophage compartments sit at pH 5.5–6.5, the Channel E occupancy window. This is compartment chemistry of the published two-channel switch — not a delivery vehicle and not an oncology protocol.
DFT first-shell metal geometries, multi-replica MD, and continuum electrostatics at pH 5.5 and 7.4. End-point free energies, where shown in the preprint, are computational and are not experimental dissociation constants.
v7 Methods ref. 20 · educational companion · v1.1 · locked kernel
The public Debye–Hückel / Yukawa continuum kernel cited in the v7 Methods section. A browser-only educational / hypothesis-generation tool that visualizes mean interaction energies between a curated public ligand set and six public receptor region-of-interest proxies under a locked, reproducible kernel — not a structural model of 5H-EAF, and not a diagnostic or therapeutic claim.
Layered disclosure: the proprietary 5H-EAF ligand is intentionally excluded from this public educational set, even though composition is described in the open preprint. Dual-use stewardship applies — protective mission framing only; no controlled technical data.
Science & data
This public site summarizes only the open ChemRxiv record (CC-BY) by Esteban A. Fridman, MD, PhD, BioChem Defense Technology. Preprints are not peer-reviewed; data may be preliminary. Binding free energies remain computational predictions — v7 reports no experimental dissociation constants. A control preparation at the default physiological pH of 7.4 is not a test of the pH gate. Full computational packages remain under appropriate agreements.
Canonical public platform paper (v7) — two-channel pH-gated mechanism, soft-metal coordination, biodefense-relevant electrostatic modeling.
Fridman EA. pH-Gated Two-Channel Histidine Nanochelant for Electrostatic Interception of Furin-Processed Polycationic Species and Soft Heavy Metals. ChemRxiv. 2026. doi:10.26434/chemrxiv.15000714/v7 (preprint, CC-BY 4.0; not peer-reviewed).
doi:10.26434/chemrxiv.15000714/v7
https://chemrxiv.org/doi/full/10.26434/chemrxiv.15000714/v7What the public record supports
Two-channel switchChannel E endosomal (pH 5.5–6.5) · Channel C physiologic (pH ~7.4)ChargeNet +4 to +5 when protonated (Channel E)pKa≈ 6.0–6.1 (five imidazole side chains)MethodsDFT · two-pH APBS/MD · continuum Yukawa (MoleculoSphere 5D)Continuum layerMoleculoSphere 5D (Yukawa / Debye–Hückel), cited in v7 MethodsChannel C metalsHg(II), Pb(II) preferred · Zn(II), Cu(I) weakly boundActionDoes not inhibit furin. Does not insert into membranes. Does not carry a cytotoxic payload.CycleReversible electrostatic switch, not a permanent steric blockScopeComputational predictions only; not experimental binding constantsDual-use stewardship
A platform that can inform biodefense research and metal detoxification is dual-use by definition. We treat that as a first-class design constraint—not a footnote.
Protective mission only
Public programs are oriented to health, environment, infrastructure resilience, and legitimate biodefense research—not offensive use.
Layered disclosure
Capability abstracts and preprint-level science publicly; sensitive implementation detail only under need-to-know agreements.
Partner diligence
Collaboration requests are screened for legitimate protective use and appropriate controls before deeper exchange.
Dual-use statement
We develop and discuss technology for identifying and reducing biological and chemical harm. We do not provide public guidance that would materially assist the creation, weaponization, or covert deployment of biological or chemical agents.
In scope (public)
v7 two-channel preprint abstract, pH-switch summary, dual-use governance language, high-level applications, and the public educational electrostatics tool (MoleculoSphere 5D).
Out of scope (public)
Agent production, weaponization steps, targeting doctrine, or export-controlled technical datasets.
Team
Founder · BioChem Defense Technology (BCDT) · Austin, TX
Physician-scientist leading computational and biophysical research on pH-gated histidine nanochelants. Corresponding author on the public v7 ChemRxiv preprint describing the two-channel 5H-EAF platform — electrostatic interception of polycationic species and soft heavy metals. Prior training and research experience includes neuro / TBI-relevant clinical science; public materials emphasize protective mission and dual-use discipline.
Contact
For research collaboration, preprint discussion, dual-use review, or capability briefings limited to non-confidential scope.
Ideal partners: labs, public agencies, biodefense programs, and industry teams with a protective mission.
Do not send: controlled technical data, classified content, or detailed agent-production information via this form.
Direct: eafridman@biochemdefensetech.com