Studies on pH-Controlled Transition of Myoglobin Capsules from Hollow to Multilayered Structures

Abstract

ABSTRACT:In this study, myoglobin biocapsules (lyophilisomes) of various types and sizes were prepared using a combination of freezing-annealing and immobilization. Hollow lyophilisomes of pure myoglobin below and above its isoelectric point were designed and changes in their secondary structure based on variations in pH were studied by circular dichroism spectroscopy and confocal laser scanning microscopy. The study results show that permeability and size of these capsules change as pH changes; besides, near the isoelectric point, large swollen multiwalled capsules are formed, which when exposed to buffers of lower pH exhibited a tendency to reverse to hollow structures. Adsorption of these capsules onto solid surfaces has been studied using quartz crystal microbalance and contact angle measurements. Thus, pH shift may be a useful post-preparation approach for stimuli-responsive modification of the surface roughness, porosity and permeability of pre-assembled polypeptide microcapsules.

Machine Learning Assisted Simultaneous Structural Profiling of Differently Charged Proteins in a Mycobacterium smegmatis Porin A (MspA) Electroosmotic Trap

“…We speculate that the EPF was more dominant on apo-myoglobin than holo-myoglobin when the applied voltage was higher than +100 mV because apo-myoglobin has a higher isoelectric point (pI = 8.5) 43 than holo-myoglobin (pI = 7.3). 56 In addition, with all other conditions identical, changing the electrolyte in trans to 1.5 M KCl also resulted in a dramatic reduction of the frequency of blocking events and a diminished escape time for both apo-and holo-myoglobin ( S9, Table S1).…”

“…However, the τ off of apo-myoglobin was only systematically extended when the voltage was increased to +100 mV, and no further extension was observed at higher voltages (Figures S8c,d and Figure S13b and Table S4). We speculate that the EPF was more dominant on apo-myoglobin than holo-myoglobin when the applied voltage was higher than +100 mV because apo-myoglobin has a higher isoelectric point (pI = 8.5) than holo-myoglobin (pI = 7.3) . In addition, with all other conditions identical, changing the electrolyte in trans to 1.5 M KCl also resulted in a dramatic reduction of the frequency of blocking events and a diminished escape time for both apo- and holo-myoglobin ( = 3640.4 ± 633.6 ms; = 1319.2 ± 321.1 ms; = 7.3 ± 1.3 ms; = 3.7 ± 0.4 ms) (Figure S9, Table S1).…”