The use of a metal–organic framework (MOF) as a support for the in situ immobilization of enzymes was explored. The MOF support, a Basolite F300‐like material, was prepared from FeCl3 and the tridentate linker trimesic acid. Immobilization of alcohol dehydrogenase, lipase, and glucose oxidase was performed in situ under mild conditions (aqueous solution, neutral pH, and at room temperature) in a rapid and facile manner with retention of activity for at least 1 week. The catalytic activities of lipase and glucose oxidase were similar to the activities of the free enzymes; with alcohol dehydrogenase, there was a substantial decrease in activity on immobilization that may arise from diffusion limitations. The approach demonstrates that a MOF material, prepared from cheap and commercially available materials, can be successively utilized to prepare stable and catalytically active biocatalysts in a rapid and facile manner.

Turbidity titrations are used to study the ion specific aggregation of hemoglobin (Hb) below and physiological salt concentration in the pH range 4.5-9.5. At a salt concentration 50 mM cations promote Hb aggregation according to the order Rb(+) > K(+) ~ Na(+) > Cs(+) > Li(+). The cation series changes if concentration is increased, becoming K(+) > Rb(+) > Na(+) > Li(+) > Cs(+) at 150 mM. We interpret the puzzling series by assuming that the kosmotropic Li(+) will bind to kosmotropic carboxylates groups-according to the law of matching water affinities (LMWA)-whereas the chaotropic Cs(+) will bind to uncharged protein patches due to its high polarizability. In fact, both mechanisms can be rationalized by invoking previously neglected ionic nonelectrostatic forces. This explains both adsorption to uncharged patches and the LMWA as a consequence of the simultaneous action of electrostatic and dispersion forces. The same interpretation applies to anions (with chaotropic anions binding to chaotropic amine groups). The implications extend beyond hemoglobin to other, still unexplained, ion specific effects in biological systems.

Lipase AK from Pseudomonas fluorescens and Lipase RM from Rhizomucor miehei were encapsulated into a zeolite imidazolate framework (ZIF‐8) by a “one‐pot” synthesis to obtain AK@ZIF‐8 and RM@ZIF‐8 biocatalysts. The effect of a high (1:40) and low (1:4) Zn/2‐methylimidazole molar ratio on the biocatalysts synthesis was investigated. The different Zn/ligand (L) ratios affected both the surface area, the loading, and the specific activity of the biocatalysts. Samples synthesized by using a high Zn/L ratio had high values of surface area whereas those obtained by using a low Zn/L ratio had higher loadings and specific activities. The decrease of pH (from 11.6 to 9.4) during the synthesis at high Zn/L ratio produced ZIF‐8 samples with features similar to those observed for low Zn/L ratio samples. The low Zn/L (1:4) ratio AK@ZIF‐8 biocatalyst retained 99 % activity after storage for 15 days at 5 °C and 40 % activity after five reaction cycles.

Lipase (Pseudomonas fluorescens) and laccase (Trametates versicolor) were encapsulated on two zeolite imidazolate framework, ZIF‐8 and ZIF‐zni, materials using a one‐pot synthesis‐immobilization method in aqueous solution at room temperature. The synthesized immobilized biocatalysts (Lip@ZIF‐8, Lip@ZIF‐zni, Lac@ZIF‐8, and Lac@ZIF‐zni) were characterized by X‐ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The enzymatic activities of the four immobilized biocatalysts were characterized via the electrochemical detection of the substrates, p‐nitrophenyl butyrate and 2,2‐azinobis‐3‐ethylbenzthiazoline‐6‐sulfonic acid. For Lip@ZIF‐8 the specific activity was 91.9 U mg−1 and 123.1 U mg−1 for Lip@ZIF‐zni, while for Lac@ZIF‐8 and Lac@ZIF‐zni, the activity was 51 U mg−1 and 163 U mg−1, respectively, confirming that laccase retains a higher level of activity when immobilized onto ZIF‐zni than on ZIF‐8. Lac@ZIF‐8 was the most stable system on storage (15 days at 5 °C), retaining 94 % of initial activity, while Lip@ZIF‐zni biocatalyst had the optimal level of reusability, retaining 40 % of initial activity after five reaction cycles.

BSA and lysozyme molecular motion at pH 7.15 is buffer-specific. Adsorption of buffer ions on protein surfaces modulates the protein surface charge and thus protein–protein interactions. Interactions were estimated by means of the interaction parameter k D obtained from plots of diffusion coefficients at different protein concentrations (D app = D 0[1 + k D C protein]) via dynamic light scattering and nuclear magnetic resonance. The obtained results agree with recent findings confirming doubts regarding the validity of the Henderson–Hasselbalch equation, which has traditionally provided a basis for understanding pH buffers of primary importance in solution chemistry, electrochemistry, and biochemistry.

The use of an in situ immobilization procedure for the immobilization of hyperhalophilic alcohol dehydrogenase in a metal organic framework material is described. The easy and rapid in situ immobilization process enables retention of activity over a broad range of pH and temperature together with a decrease in the halophilicity of the enzyme. The catalytic activity of the immobilized enzyme was studied in nonaqueous solvent mixtures with the highest retention of activity in aqueous solutions of methanol and acetonitrile. The approach demonstrates that this immobilization method can be extended to hyperhalophilic enzymes with enhancements in activity and stability.

This contribution is dedicated to Prof. Lo Gorton on the occasion of his 70 th birthday in recognition of his outstanding contributions to the field of (bio)electrochemistry over several decadesThe immobilization of bilirubin oxidase (BOD) on macroporous gold electrodes for the optimization of bioelectrocatalytic activity is described. A bilirubin oxidase mutant S362C (cys-BOD) engineered with a cysteine residue located on purpose at the enzyme surface close to the T1 active center was used. It allows the attachment in one-step of a self-assembled monolayer of the enzyme to gold through a reaction between the thiol group of the cysteine residue and the metal surface. BOD immobilization of wild type and S362C mutant in macroporous gold electrodes allowed high retention of activity and perfect control of the overall BOD loading due to the fine-tuning of the macroporous structure. The macroporous arrangement together with the use of cys-BOD makes these rationally designed enzyme-modified electrodes very promising candidates for high-performance bioelectrocatalytic devices with improved activity and stability. long-term stability of cys-BODÀ Au is interpreted as the consequence of the covalent bond between the enzyme and the gold structure, thus avoiding enzyme leaching even after several days of incubation.

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights  The effect of electrolytes in bioelectrochemistry is presented.  The Hofmeister effect and the most recent experimental and theoretical work on specific ion effects are described.  The research challenges and the importance of choosing the most appropriate electrolyte for bionsensors and biofuel cells have been reviewed.