Synthesis of Lysozyme–Metallacarborane Conjugates and the Effect of Boron Cluster Modification on Protein Structure and Function

Abstract

Two complementary methods, "in solution" and "in solid state", for the synthesis of lysozyme modified with metallacarborane (cobalt bis(dicarbollide), Co(C2 B9 H11 )2 (2-) ) were developed. As metallacarborane donors, oxonium adducts of cobalt bis(dicarbollide) and 1,4-dioxane or tetrahydropyran were used. The physicochemical and biochemical properties of the obtained lysozyme-metallacarborane conjugates were studied for changes in secondary and tertiary structure, aggregation behavior, and biological activity. Only minor changes in primary, secondary, and tertiary protein structure were observed, caused by the single substitution of metallacarborane on lysozyme. However, the modification produced significant changes in lysozyme enzymatic activity and a tendency toward time- and temperature-dependent aggregation.

Charge‐Compensated Metallacarborane Building Blocks for Conjugation with Peptides

“…The 1 H, 11 B, and 13 CNMR spectra were recorded with aB ruker AVANCE DRX 400 spectrometer.T he chemical shifts of 1 H, 11 B, and 13 Ca re reported in parts per million at 400. 13,128.38, and 100.63 MHz, respectively,w ith tetramethylsilane as internal standard and referencing to the unified scale. [22] Substituted boron atoms could be assigned by comparison of 11 Ba nd 11 B{ 1 H} NMR spectra.…”

“…[12] In view of this large number of peptides,i ta ppears surprising that the cobalt bis(dicarbollide) anion 1 has never been incorporated into any tumor-selective peptided espite obvious possible advantages. [13] The high stabilityr elative to polyhedral boron compounds, the strongl ipophilicity (givingr ise to hydrophobic peptide-receptor interactions), the hydridic shell (whichf acilitatesu nusualm olecular interactions unknown in traditional organic scaffolds), and the large number of boron atomsm ake anion 1 an interesting moiety,i np articularf or applications in BNCT. [2a,b] The biologically active derivatives of cobaltb is(dicarbollide) that have previously been studied [3][4][5][6]13] have exclusively been obtained by ring-opening reactions of cyclic oxonium derivatives 2 (Scheme 1).…”

Preparing (Metalla)carboranes for Nanomedicine

“…As until today, the implications of protein coronas on the biological performance of (metalla)carboranes and borates as colloidal aggregators have hardly been studied, but some publications on metallacarborane-protein conjugates deal with adsorbed protein phaenomena (see, e. g., refs. [158] and [179]). The following sections will thus highlight selected effects of protein coronas on immune toxicity, active targeting, and cellular uptake and clearance pathways, and appropriate examples from the (metalla)carboranes literature will be briefly discussed.…”

“…Furthermore, loading capacity and binding sites are also determined using mass spectrometry methods or Western blot analyses, often in combination with chromatographic or electrophoretic separations, specifically for peptide, protein or enzyme conjugates. [162,176,[179][180][181] A rather atypical example is one of the latest works by Ventura, Teixidor and co-workers (2019) on the interaction between BSA and Na[COSAN]. [158] They used DLS, zeta potential and far-UV circular dichroism (CD) spectroscopy to infer saturation stoichiometry and co-assembly motifs of BSA-COSAN nanostructures, concluding that COSAN molecules, when used in large excess (100 ×) over BSA, can form a sort of protective crown around the BSA molecule, shielding it from thermal and light-induced denaturation and acetylation.…”

Cation-sensitive compartmentalization in metallacarborane containing polymer nanoparticles

“…It was demonstrated that they provide an unusual interaction potential resulting in self-assembly in solution 5,6 and complexation with various nanosystems. [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] They are utilized, for example, for ion extraction 26 and recently also in medicinal chemistry. [27][28][29][30][31][32][33][34][35][36][37][38] As regards medical applications, our interest is targeted to the preparation of stimuli-responsive hybrid nanosystems consisting of a nano-organized polymer matrix with embedded metallacarborane clusters, [39][40][41][42] which would lead to biocompatible vessels for drug-delivery purposes.…”