Competing Interactions in Hierarchical Porphyrin Self-Assembly Introduce Robustness in Pathway Complexity.

Pathway complexity in supramolecular polymerization has recently sparked interest as a method to generate complex material behavior. The response of these systems relies on the existence of a metastable, kinetically trapped state. In this work, we show that strong switch-like behavior in supramolecular polymers can also be achieved through the introduction of competing aggregation pathways. This behavior is illustrated with the supramolecular polymerization of a porphyrin-based monomer at various concentrations, solvent compositions, and temperatures. It is found that the monomers aggregate via an isodesmic mechanism in weakly coupled J-type aggregates at intermediate solvent quality and temperature, followed by nucleated H-aggregates at lower solvent qualities and temperatures. At further increased thermodynamic driving forces, such as high concentration and low temperature, the H-aggregates can form hierarchical superhelices. Our mathematical models show that, contrary to a single-pathway polymerization, the existence of the isodesmic aggregation pathway buffers the free monomer pool and renders the nucleation of the H-aggregates insensitive to concentration changes in the limit of high concentrations. We also show that, at a given temperature or solvent quality, the thermodynamically stable aggregate morphology can be selected by controlling the remaining free external parameter. As a result, the judicious application of pathway complexity allows us to synthesize a diverse set of materials from only a single monomer. We envision that the engineering of competing pathways can increase the robustness in a wide variety of supramolecular polymer materials and lead to increasingly versatile applications.

Acute hemolytic transfusion reaction due to a warm reactive anti-A1.

BACKGROUND: Anti-A1 are regularly observed by reverse testing and are generally considered clinically irrelevant. For compatibility testing and the selection of blood, we use the type-and-screen (T&S) strategy, in which ABO confirmation of patients with a definitive blood group is performed by forward grouping only. Because anti-A1 seem clinically irrelevant, it is our policy to provide group A blood in patients with an anti-A1 . STUDY DESIGN AND METHODS: This is a case report of a 96-year-old woman who died shortly after transfusion of blood group A red blood cells (RBCs). She was known to have blood group A2 with an anti-A1 and the absence of other RBC antibodies. Directly after starting transfusion, acute dyspnea was observed, while other clinical signs for a transfusion reaction were absent. In the laboratory, indications for a severe hemolytic transfusion reaction (HTR) triggered serologic investigations and complement deposition experiments. RESULTS: Analyses revealed that the anti-A1 was present as a high-titer IgM class immunoglobulin that induced complement deposition on A1 RBCs. The anti-A1 reacted in a wide temperature amplitude up to 37°C with A1 RBCs, while weak agglutination was observed with A2 RBCs at room temperature. CONCLUSION: A pretransfusion detectable anti-A1 caused a severe HTR that, in view of the rapid onset of clinical symptoms and concomitant deterioration, contributed to the death of the patient. Considering its clinical significance in this case, we encourage an unambiguous procedure for patients with an anti-A1 , especially when T&S is used for donor RBC selection.

Explainable Machine Learning Models for Rapid Risk Stratification in the Emergency Department: A Multicenter Study.

BACKGROUND: Risk stratification of patients presenting to the emergency department (ED) is important for appropriate triage. Diagnostic laboratory tests are an essential part of the workup and risk stratification of these patients. Using machine learning, the prognostic power and clinical value of these tests can be amplified greatly. In this study, we applied machine learning to develop an accurate and explainable clinical decision support tool model that predicts the likelihood of 31-day mortality in ED patients (the RISKINDEX). This tool was developed and evaluated in four Dutch hospitals. METHODS: Machine learning models included patient characteristics and available laboratory data collected within the first 2 h after ED presentation, and were trained using 5 years of data from consecutive ED patients from the Maastricht University Medical Center (Maastricht), Meander Medical Center (Amersfoort), and Zuyderland Medical Center (Sittard and Heerlen). A sixth year of data was used to evaluate the models using area under the receiver-operating-characteristic curve (AUROC) and calibration curves. The Shapley additive explanations (SHAP) algorithm was used to obtain explainable machine learning models. RESULTS: The present study included 266 327 patients with 7.1 million laboratory results available. Models show high diagnostic performance with AUROCs of 0.94, 0.98, 0.88, and 0.90 for Maastricht, Amersfoort, Sittard and Heerlen, respectively. The SHAP algorithm was utilized to visualize patient characteristics and laboratory data patterns that underlie individual RISKINDEX predictions. CONCLUSIONS: Our clinical decision support tool has excellent diagnostic performance in predicting 31-day mortality in ED patients. Follow-up studies will assess whether implementation of these algorithms can improve clinically relevant end points.

Photocontrol over cooperative porphyrin self-assembly with phenylazopyridine ligands.

The cooperative self-assembly of chiral zinc porphyrins is regulated by a photoresponsive phenylazopyridine ligand. Porphyrin stacks depolymerize into dimers upon axial ligation and the strength of the coordination is regulated by its photoinduced isomerization, which shows more than 95 % conversion ratio for both photostationary states.

Effect of stereogenic centers on the self-sorting, depolymerization, and atropisomerization kinetics of porphyrin-based aggregates.

We present our results on the mixing of different porphyrin molecules in supramolecular assemblies. Herein, chiral amplification experiments reveal the subtle role of the structural (mis)match between these monomers. We show that according to the "sergeant-and-soldiers" principle, a chiral porphyrin "sergeant" efficiently mixes with achiral "soldiers" in the same helical aggregate and strongly biases its handedness. However, when we mix two porphyrin enantiomers in a majority-rules experiment, no chiral amplification is observed at all, which is due to their narcissistic self-sorting into conglomerate-like aggregates. The mixing between two enantiomers in the same stack only occurs in a diluted-majority-rules experiment, in which enantiomeric mixtures of sergeants are diluted with achiral soldiers. The different outcomes of these chiral amplification phenomena are verified by modeling studies that reveal high mismatch penalties, which are ascribed to the high stereocenter loading of 12 methyl groups onto the monomers. Mixed-metal chiral amplification experiments between copper- and zinc-porphyrins show the same distinction in their mixing behavior, which is further supported by fluorescence measurements. The selective removal of chiral Zn-porphyrins from these mixed-metal systems is performed with the Lewis base quinuclidine that depolymerizes the Zn-porphyrins upon axial ligation. This extraction process proceeds at different time scales, depending on the mixed state: slow extraction kinetics for the mixed sergeant-and-soldiers and diluted-majority-rules systems and an instant extraction for the phase-separated majority-rules system. By simultaneously monitoring the supramolecular chirality during extraction, a chiral memory effect is observed for both mixed systems that show slow extraction kinetics. For the sergeant-and-soldiers system, the remaining supramolecular backbone contains achiral monomers only, which give rise to a long lasting chiral memory with slow, entropy-driven atropisomerization. Yet in case of the diluted-majority-rules system, the remaining backbone contains a mixture of achiral and chiral monomers in its unpreferred helicity; giving rise to a short chiral memory, in which the fast atropisomerization is enthalpy-driven due to the high mismatch penalty.

Chiral memory via chiral amplification and selective depolymerization of porphyrin aggregates.

Chiral memory at the supramolecular level is obtained via a new approach using chiral Zn porphrins and achiral Cu porphyrins. In a "sergeant-and-soldiers" experiment, the Zn "sergeant" transfers its own chirality to Cu "soldiers" and, after chiral amplification, the "sergeant" is removed from the coaggregates by axial ligation with a Lewis base. After this extraction, the preferred helicity observed for the aggregates containing achiral Cu porphyrins reveals a chiral memory effect that is stable and can be erased and partially restored upon subsequent heating and cooling.

Rapid phenotype hemoglobin screening by high-resolution mass spectrometry on intact proteins.

BACKGROUND: Given the excellent performance of modern mass spectrometers, their clinical application for the analysis of macromolecules is a growing field of interest. This principle is explored by hemoglobin analysis, which is a representative example by its molecular weight and clinical relevance in e.g. screening programs for thalassemia and hemoglobin variants. Considering its abundance and cellular containment, pre-analysis is significantly reduced allowing for essential rapid acquisitions. METHODS: By parallel analysis of routine diagnostics for hemoglobin variants and thalassemia, we acquired samples of adults who were consented for hemoglobinopathy screening in our clinical laboratory. The pre-analytical process comprised of red cell lysis only; without further digestion and purification steps, the samples were directly injected in an electrospray ionization quadrupole time-of-flight setup and the intact proteins were analyzed by flow injection analysis. After optimization of process parameters, the deconvoluted mass spectra revealed the presence of α- and ß-globulins. The reference ranges for the average mass of both globulins and their intensity ratio (α/ß-ratio) were deduced from a disease-free subgroup and patients with a hemoglobinopathy were compared. RESULTS: The α/ß-ratio is a poor marker for thalassemia patients, yet deviant α/ß-ratios are found for patients with a hemoglobin variant. Mass deviations down to 1Da can be resolved; even if the patient suffers from a heterozygotic disorder, the average mass is found outside the established reference interval. CONCLUSIONS: Although subjects with mild thalassemia were not detected, all patients with a hemoglobin variant were resolved by top-down mass spectrometry using the average globulin mass and the α/ß-ratio as screening parameters.

Controlled perturbation of the thermodynamic equilibrium by microfluidic separation of porphyrin-based aggregates in a multi-component self-assembling system.

In a microfluidic H-cell, a multi-component self-assembled system is brought out-of-equilibrium by changing the bimodal composition of porphyrin stacks and pyridine-capped dimers. Driven by their different diffusivities, diffusion-controlled separation in methylcyclohexane reveals different compositions when detected in-line and off-line, which demonstrates the kinetic behaviour of this metastable system. The microfluidic technique also proves to be highly equipped to determine diffusion constants of the different assemblies.