Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 99
Filter
Add more filters










Publication year range
1.
Cont Lens Anterior Eye ; : 102249, 2024 Jun 05.
Article in English | MEDLINE | ID: mdl-38839478

ABSTRACT

PURPOSE: Contact lenses can be contaminated with various microorganisms, including pathogenic yeasts of the genus Candida, which are known for their ability to adhere to abiotic surfaces, including plastic materials used for various medical purposes. Microbial contamination of the lenses can lead to infection of the wearer's eyes. The purpose of this study was to simulate the contamination of contact lenses with C. albicans and C. parapsilosis, analyze the interaction of the microorganisms with the lens material, and optimize the protocol for PCR-based analysis of the microbial agents responsible for lens contamination. METHODS: Hilafilcon lenses were exposed to C. albicans and C. parapsilosis cultures, washed, and examined for their ability to further spread the contamination. Scanning electron microscopy was used to analyze the attachment of yeast cells to the lenses. Infrared spectroscopy was used to examine the potential changes in the lens material due to Candida contamination. The protocol for DNA isolation from contaminated lenses was established to enable PCR analysis of microbes attached to the lenses. RESULTS: Hilafilcon lenses contaminated with Candida were able to spread the contamination even after washing with saline or with a commercial cleaning solution. In the present experimental settings, the yeasts did not grow into the lenses but began to form biofilms on the surface. However, the ability of the lenses to retain water was altered. The PCR-based protocol could be used to help identify the type of contamination of contact lenses. CONCLUSION: Once contaminated with Candida albicans or Candida parapsilosis, Hilafilcon contact lenses are difficult to clean. Yeasts began to form biofilms on lens surfaces.

2.
ACS Chem Biol ; 19(6): 1243-1249, 2024 Jun 21.
Article in English | MEDLINE | ID: mdl-38747804

ABSTRACT

Nicotinamide adenine dinucleotide (NAD) is a critical component of the cellular metabolism and also serves as an alternative 5' cap on various RNAs. However, the function of the NAD RNA cap is still under investigation. We studied NAD capping of RNAs in HIV-1-infected cells because HIV-1 is responsible for the depletion of the NAD/NADH cellular pool and causing intracellular pellagra. By applying the NAD captureSeq protocol to HIV-1-infected and uninfected cells, we revealed that four snRNAs (e.g., U1) and four snoRNAs lost their NAD cap when infected with HIV-1. Here, we provide evidence that the presence of the NAD cap decreases the stability of the U1/HIV-1 pre-mRNA duplex. Additionally, we demonstrate that reducing the quantity of NAD-capped RNA by overexpressing the NAD RNA decapping enzyme DXO results in an increase in HIV-1 infectivity. This suggests that NAD capping is unfavorable for HIV-1 and plays a role in its infectivity.


Subject(s)
HIV Infections , HIV-1 , NAD , RNA, Small Nuclear , RNA, Small Nucleolar , Humans , NAD/metabolism , RNA, Small Nucleolar/metabolism , RNA, Small Nucleolar/genetics , RNA, Small Nuclear/metabolism , HIV Infections/virology , HIV Infections/metabolism , RNA Caps/metabolism
3.
Spectrochim Acta A Mol Biomol Spectrosc ; 318: 124478, 2024 Oct 05.
Article in English | MEDLINE | ID: mdl-38788502

ABSTRACT

X-ray diffraction is a commonly used technique in the pharmaceutical industry for the determination of the atomic and molecular structure of crystals. However, it is costly, sometimes time-consuming, and it requires a considerable degree of expertise. Vibrational circular dichroism (VCD) spectroscopy resolves these limitations, while also exhibiting substantial sensitivity to subtle modifications in the conformation and molecular packaging in the solid state. This study showcases VCD's ability to differentiate between various crystal structures of the same molecule (polymorphs, cocrystals). We examined the most effective approach for producing high-quality spectra and unveiled the intricate link between structure and spectrum via quantum-chemical computations. We rigorously assessed, using alanine as a model compound, multiple experimental conditions on the resulting VCD spectra, with the aim of proposing an optimal and efficient procedure. The proposed approach, which yields reliable, reproducible, and artifact-free results with maximal signal-to-noise ratio, was then validated using a set comprising of three amino acids (serine, alanine, tyrosine), one hydroxy acid (tartaric acid), and a monosaccharide (ribose) to mimic active pharmaceutical components. Finally, the optimized approach was applied to distinguish three polymorphs of the antiviral drug sofosbuvir and its cocrystal with piperazine. Our results indicate that solid-state VCD is a prompt, cost-effective, and easy-to-use technique to identify crystal structures, demonstrating potential for application in pharmaceuticals. We also adapted the cluster and transfer approach to calculate the spectral properties of molecules in a periodic crystal environment. Our findings demonstrate that this approach reliably produces solid-state VCD spectra of model compounds. Although for large molecules with many atoms per unit cell, such as sofosbuvir, this approach has to be simplified and provides only a qualitative match, spectral calculations, and energy analysis helped us to decipher the observed differences in the experimental spectra of sofosbuvir.


Subject(s)
Circular Dichroism , Crystallization , Sofosbuvir , Sofosbuvir/chemistry , Vibration , Models, Molecular , Antiviral Agents/chemistry
4.
Commun Chem ; 7(1): 114, 2024 May 25.
Article in English | MEDLINE | ID: mdl-38796536

ABSTRACT

Peptide-like foldamers controlled by normal amide backbone hydrogen bonding have been extensively studied, and their folding patterns largely rely on configurational and conformational constraints induced by the steric properties of backbone substituents at appropriate positions. In contrast, opportunities to influence peptide secondary structure by functional groups forming individual hydrogen bond networks have not received much attention. Here, peptide-like foldamers consisting of alternating α,ß,γ-triamino acids 3-amino-4-(aminomethyl)-2-methylpyrrolidine-3-carboxylate (AAMP) and natural amino acids glycine and alanine are reported, which were obtained by solution phase peptide synthesis. They form ordered secondary structures, which are dominated by a three-dimensional bridged triazaspiranoid-like hydrogen bond network involving the non-backbone amino groups, the backbone amide hydrogen bonds, and the relative configuration of the α,ß,γ-triamino and α-amino acid building blocks. This additional stabilization leads to folding in both nonpolar organic as well as in aqueous environments. The three-dimensional arrangement of the individual foldamers is supported by X-ray crystallography, NMR spectroscopy, chiroptical methods, and molecular dynamics simulations.

5.
ACS Omega ; 9(6): 7043-7052, 2024 Feb 13.
Article in English | MEDLINE | ID: mdl-38371788

ABSTRACT

The stereoselective reduction of the steroidal 4-ene-3-ketone moiety (enone) affords the 5ß-steroid backbone that is a key structural element of biologically important neuroactive steroids. Neurosteroids have been currently studied as novel and potent central nervous system drug-like compounds for the treatment of, e.g., postpartum depression. As a green methodology, we studied the palladium-catalyzed hydrogenation of steroidal 4-ene-3-ketones in the presence of ionic liquids derived from natural carboxylic acids. The hydrogenation proceeds with improved 5ß-selectivity in the presence of tetrabutylammonium carboxylates as additives compared to the exclusive use of an organic solvent. Under optimal conditions, using tetrabutylammonium d-mandelate, the reduction of testosterone led to 5ß-dihydrotestosterone in high yield and stereoselectivity and no byproduct formation was observed. Moreover, the catalyst could be recycled. The presence of additional substituents on the steroid backbone showed a significant effect on the 5ß-selectivity.

6.
Chem Sci ; 15(2): 594-608, 2024 Jan 03.
Article in English | MEDLINE | ID: mdl-38179543

ABSTRACT

Certain peptide sequences, some of them as short as amino acid triplets, are significantly overpopulated in specific secondary structure motifs in folded protein structures. For example, 74% of the EAM triplet is found in α-helices, and only 3% occurs in the extended parts of proteins (typically ß-sheets). In contrast, other triplets (such as VIV and IYI) appear almost exclusively in extended parts (79% and 69%, respectively). In order to determine whether such preferences are structurally encoded in a particular peptide fragment or appear only at the level of a complex protein structure, NMR, VCD, and ECD experiments were carried out on selected tripeptides: EAM (denoted as pro-'α-helical' in proteins), KAM(α), ALA(α), DIC(α), EKF(α), IYI(pro-ß-sheet or more generally, pro-extended), and VIV(ß), and the reference α-helical CATWEAMEKCK undecapeptide. The experimental data were in very good agreement with extensive quantum mechanical conformational sampling. Altogether, we clearly showed that the pro-helical vs. pro-extended propensities start to emerge already at the level of tripeptides and can be fully developed at longer sequences. We postulate that certain short peptide sequences can be considered minimal "folding seeds". Admittedly, the inherent secondary structure propensity can be overruled by the large intramolecular interaction energies within the folded and compact protein structures. Still, the correlation of experimental and computational data presented herein suggests that the secondary structure propensity should be considered as one of the key factors that may lead to understanding the underlying physico-chemical principles of protein structure and folding from the first principles.

7.
Nucleic Acids Res ; 51(21): 11428-11438, 2023 Nov 27.
Article in English | MEDLINE | ID: mdl-37870471

ABSTRACT

We designed and synthesized a set of four 2'-deoxyribonucleoside 5'-O-triphosphates (dNTPs) derived from 5-substituted pyrimidines and 7-substituted 7-deazapurines bearing anionic substituents (carboxylate, sulfonate, phosphonate, and phosphate). The anion-linked dNTPs were used for enzymatic synthesis of modified and hypermodified DNA using KOD XL DNA polymerase containing one, two, three, or four modified nucleotides. The polymerase was able to synthesize even long sequences of >100 modified nucleotides in a row by primer extension (PEX). We also successfully combined two anionic and two hydrophobic dNTPs bearing phenyl and indole moieties. In PCR, the combinations of one or two modified dNTPs gave exponential amplification, while most of the combinations of three or four modified dNTPs gave only linear amplification in asymmetric PCR. The hypermodified ONs were successfully re-PCRed and sequenced by Sanger sequencing. Biophysical studies including hybridization, denaturation, CD spectroscopy and molecular modelling and dynamics suggest that the presence of anionic modifications in one strand decreases the stability of duplexes while still preserving the B-DNA conformation, whilst the DNA hypermodified in both strands adopts a different secondary structure.


Subject(s)
DNA , Nucleotides , DNA/chemistry , Nucleotides/chemistry , DNA-Directed DNA Polymerase/metabolism , Base Sequence , Pyrimidines
8.
ACS Infect Dis ; 9(10): 1918-1931, 2023 Oct 13.
Article in English | MEDLINE | ID: mdl-37728236

ABSTRACT

A collaborative, open-science team undertook discovery of novel small molecule inhibitors of the SARS-CoV-2 nsp16-nsp10 2'-O-methyltransferase using a high throughput screening approach with the potential to reveal new inhibition strategies. This screen yielded compound 5a, a ligand possessing an electron-deficient double bond, as an inhibitor of SARS-CoV-2 nsp16 activity. Surprisingly, X-ray crystal structures revealed that 5a covalently binds within a previously unrecognized cryptic pocket near the S-adenosylmethionine binding cleft in a manner that prevents occupation by S-adenosylmethionine. Using a multidisciplinary approach, we examined the mechanism of binding of compound 5a to the nsp16 cryptic pocket and developed 5a derivatives that inhibited nsp16 activity and murine hepatitis virus replication in rat lung epithelial cells but proved cytotoxic to cell lines canonically used to examine SARS-CoV-2 infection. Our study reveals the druggability of this newly discovered SARS-CoV-2 nsp16 cryptic pocket, provides novel tool compounds to explore the site, and suggests a new approach for discovery of nsp16 inhibition-based pan-coronavirus therapeutics through structure-guided drug design.


Subject(s)
COVID-19 , SARS-CoV-2 , Mice , Rats , Animals , SARS-CoV-2/metabolism , S-Adenosylmethionine/chemistry , S-Adenosylmethionine/metabolism , Methyltransferases
9.
J Org Chem ; 88(11): 6573-6587, 2023 Jun 02.
Article in English | MEDLINE | ID: mdl-37219972

ABSTRACT

Three symmetrically and three unsymmetrically substituted cibalackrot (7,14-diphenyldiindolo[3,2,1-de:3',2',1'-ij][1,5]naphthyridine-6,13-dione, 1) dyes carrying two derivatized phenyl rings have been synthesized as candidates for molecular electronics and especially for singlet fission, a process of interest for solar energy conversion. Solution measurements provided singlet and triplet excitation energies and fluorescence yields and lifetimes; conformational properties were analyzed computationally. The molecular properties are close to ideal for singlet fission. However, crystal structures, obtained by single-crystal X-ray diffraction (XRD), are rather similar to those of the polymorphs of solid 1, in which the formation of a charge-separated state followed by intersystem crossing, complemented with excimer formation, outcompetes singlet fission. Results of calculations by the approximate SIMPLE method suggest which ones among the solid derivatives are the best candidates for singlet fission, but it appears difficult to change the crystal packing in a desirable direction. We also describe the preparation of three specifically deuteriated versions of 1, expected to help sort out the mechanism of fast intersystem crossing in its charge-separated state.

10.
J Am Chem Soc ; 145(21): 11599-11610, 2023 May 31.
Article in English | MEDLINE | ID: mdl-37129470

ABSTRACT

Helical bilayer nanographenes (HBNGs) are chiral π-extended aromatic compounds consisting of two π-π stacked hexabenzocoronenes (HBCs) joined by a helicene, thus resembling van der Waals layered 2D materials. Herein, we compare [9]HBNG, [10]HBNG, and [11]HBNG helical bilayers endowed with [9], [10], and [11]helicenes embedded in their structure, respectively. Interestingly, the helicene length defines the overlapping degree between the two HBCs (number of benzene rings involved in π-π interactions between the two layers), being 26, 14, and 10 benzene rings, respectively, according to the X-ray analysis. Unexpectedly, the electrochemical study shows that the lesser π-extended system [9]HBNG shows the strongest electron donor character, in part by interlayer exchange resonance, and more red-shifted values of emission. Furthermore, [9]HBNG also shows exceptional chiroptical properties with the biggest values of gabs and glum (3.6 × 10-2) when compared to [10]HBNG and [11]HBNG owing to the fine alignment in the configuration of [9]HBNG between its electric and magnetic dipole transition moments. Furthermore, spectroelectrochemical studies as well as the fluorescence spectroscopy support the aforementioned experimental findings, thus confirming the strong impact of the helicene length on the properties of this new family of bilayer nanographenes.

11.
Nanoscale ; 15(4): 1542-1553, 2023 Jan 27.
Article in English | MEDLINE | ID: mdl-36383069

ABSTRACT

Fully aromatic helicenes are attractive building blocks for the construction of inherently chiral π-conjugated macrocyclic nanocarbons. These hitherto rare molecular architectures are envisaged to exhibit remarkable (chir)optical properties, self-assembly, charge/spin transport, induced ring current or a fascinating Möbius topology. Here the synthesis of helically chiral macrocycles that combine angular dibenzo[5]helicene units as corners and linear trans-stilbene-4,4'-diyl linkers as edges is reported. By subjecting a racemic or enantiopure divinyl derivative of dibenzo[5]helicene to olefin metathesis, which was catalysed by a 2nd generation Piers catalyst under kinetic control, a π-conjugated helicene cyclic trimer (33%) and a tetramer (22%) were obtained, which were separated by GPC. Combining racemic/asymmetric synthesis with the resolution of enantiomers/diastereomers by SFC/HPLC on a chiral column, both homochiral (+)-(M,M,M)/(-)-(P,P,P) and heterochiral (+)-(M,M,P)/(-)-(M,P,P) stereoisomers of the helicene cyclic trimer could be obtained in an enantio- and diastereomerically enriched form. The complete energy profile of their interconversion was compiled on the basis of kinetic measurements and numerical solution of the proposed kinetic model. In equilibrium, the heterochiral diastereomer predominates over the homochiral one (ca. 75 : 25 at 76 °C). π-Conjugation along a large, twisted circuit in the helicene cyclic trimer is rather disrupted, stabilising this formally antiaromatic molecule. Using an optimised PeakForce mode of ambient AFM, the self-assembly of otherwise highly mobile stereoisomers of the helicene cyclic trimer on the HOPG surface could be studied. Irrespective of the stereochemistry, strong preferences for the edge-to-edge interaction of these macrocycles were found to form very long parallel 1D molecular stripes in ordered 2D nanocrystals, a result also supported by molecular dynamics simulations. Six trityl groups, initially introduced to the macrocycle to enhance solubility, serve as a key "molecular Velcro" system in the self-assembly of macrocycles to maximise their mutual van der Waals interactions.

12.
Chem Commun (Camb) ; 58(91): 12732-12735, 2022 Nov 15.
Article in English | MEDLINE | ID: mdl-36314481

ABSTRACT

A series of regioisomeric push-pull amino-nitro [6]helicenes and a related [7]helicene derivative were prepared and their racemates resolved into enantiomers. Compared to the parent helicenes, they exhibit red-shifted UV-Vis spectra, pronounced dipole moments, altered chiroptical properties such as remarkable optical rotatory power, and can form nanocrystalline Langmuir-Blodgett films.


Subject(s)
Polycyclic Compounds , Stereoisomerism
13.
Int J Mol Sci ; 23(11)2022 May 31.
Article in English | MEDLINE | ID: mdl-35682881

ABSTRACT

We studied the kinetics of the reaction of N-acetyl-l-cysteine (NAC or RSH) with cupric ions at an equimolar ratio of the reactants in aqueous acid solution (pH 1.4−2) using UV/Vis absorption and circular dichroism (CD) spectroscopies. Cu2+ showed a strong catalytic effect on the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) radical (ABTSr) consumption and autoxidation of NAC. Difference spectra revealed the formation of intermediates with absorption maxima at 233 and 302 nm (ε302/Cu > 8 × 103 M−1 cm−1) and two positive Cotton effects centered at 284 and 302 nm. These intermediates accumulate during the first, O2-independent, phase of the NAC autoxidation. The autocatalytic production of another chiral intermediate, characterized by two positive Cotton effects at 280 and 333 nm and an intense negative one at 305 nm, was observed in the second reaction phase. The intermediates are rapidly oxidized by added ABTSr; otherwise, they are stable for hours in the reaction solution, undergoing a slow pH- and O2-dependent photosensitive decay. The kinetic and spectral data are consistent with proposed structures of the intermediates as disulfide-bridged dicopper(I) complexes of types cis-/trans-CuI2(RS)2(RSSR) and CuI2(RSSR)2. The electronic transitions observed in the UV/Vis and CD spectra are tentatively attributed to Cu(I) → disulfide charge transfer with an interaction of the transition dipole moments (exciton coupling). The catalytic activity of the intermediates as potential O2 activators via Cu(II) peroxo-complexes is discussed. A mechanism for autocatalytic oxidation of Cu(I)−thiolates promoted by a growing electronically coupled −[CuI2(RSSR)]n− polymer is suggested. The obtained results are in line with other reported observations regarding copper-catalyzed autoxidation of thiols and provide new insight into these complicated, not yet fully understood systems. The proposed hypotheses point to the importance of the Cu(I)−disulfide interaction, which may have a profound impact on biological systems.


Subject(s)
Acetylcysteine , Sulfhydryl Compounds , Antioxidants , Copper/chemistry , Disulfides , Oxidation-Reduction , Oxygen/chemistry , Reactive Oxygen Species
14.
Mol Biol Evol ; 39(3)2022 03 02.
Article in English | MEDLINE | ID: mdl-35137196

ABSTRACT

RNA-peptide/protein interactions have been of utmost importance to life since its earliest forms, reaching even before the last universal common ancestor (LUCA). However, the ancient molecular mechanisms behind this key biological interaction remain enigmatic because extant RNA-protein interactions rely heavily on positively charged and aromatic amino acids that were absent (or heavily under-represented) in the early pre-LUCA evolutionary period. Here, an RNA-binding variant of the ribosomal uL11 C-terminal domain was selected from an approximately 1010 library of partially randomized sequences, all composed of ten prebiotically plausible canonical amino acids. The selected variant binds to the cognate RNA with a similar overall affinity although it is less structured in the unbound form than the wild-type protein domain. The variant complex association and dissociation are both slower than for the wild-type, implying different mechanistic processes involved. The profile of the wild-type and mutant complex stabilities along with molecular dynamics simulations uncovers qualitative differences in the interaction modes. In the absence of positively charged and aromatic residues, the mutant uL11 domain uses ion bridging (K+/Mg2+) interactions between the RNA sugar-phosphate backbone and glutamic acid residues as an alternative source of stabilization. This study presents experimental support to provide a new perspective on how early protein-RNA interactions evolved, where the lack of aromatic/basic residues may have been compensated by acidic residues plus metal ions.


Subject(s)
Amino Acids , RNA , Amino Acids/genetics , Ions , Molecular Dynamics Simulation , RNA/genetics
15.
J Magn Reson ; 336: 107149, 2022 03.
Article in English | MEDLINE | ID: mdl-35121491

ABSTRACT

Conventional Nuclear Magnetic Resonance (NMR) analysis relies on H-H/C-H interactions. However, these interactions are sometimes insufficient for an accurate and precise NMR analysis. In this study, we show that 31P NMR parameters can provide critical structural insights into the stereochemistry of phosphorus-containing compounds. For this purpose, we prepared a set of model phosphorus-based proline derivatives, separated diastereoisomers, and determined their absolute configuration by single-crystal X-ray diffraction. After supplementing these results by electronic circular dichroism (ECD) spectroscopy, we combined experimental data and DFT calculations from our model compounds to perform a detailed conformational analysis, thereby determining their relative configuration. Overall, our findings establish an experimental paradigm for combining 31P NMR spectroscopy with other optical methods to facilitate the stereochemical analysis of phosphorus-containing compounds.


Subject(s)
Phosphorus , Circular Dichroism , Magnetic Resonance Spectroscopy , Molecular Conformation , Stereoisomerism
16.
Protein Sci ; 30(8): 1653-1666, 2021 08.
Article in English | MEDLINE | ID: mdl-33969912

ABSTRACT

Most of the structural proteins known today are composed of domains that carry their own functions while keeping their structural properties. It is supposed that such domains, when taken out of the context of the whole protein, can retain their original structure and function to a certain extent. Information on the specific functional and structural characteristics of individual domains in a new context of artificial fusion proteins may help to reveal the rules of internal and external domain communication. Moreover, this could also help explain the mechanism of such communication and address how the mutual allosteric effect plays a role in a such multi-domain protein system. The simple model system of the two-domain fusion protein investigated in this work consisted of a well-folded PDZ3 domain and an artificially designed small protein domain called Tryptophan Cage (TrpCage). Two fusion proteins with swapped domain order were designed to study their structural and functional features as well as their biophysical properties. The proteins composed of PDZ3 and TrpCage, both identical in amino acid sequence but different in composition (PDZ3-TrpCage, TrpCage-PDZ3), were studied using circualr dichroism (CD) spectrometry, analytical ultracentrifugation, and molecular dynamic simulations. The biophysical analysis uncovered different structural and denaturation properties of both studied proteins, revealing their different unfolding pathways and dynamics.


Subject(s)
PDZ Domains , Recombinant Fusion Proteins , Tryptophan , Amino Acid Sequence , Molecular Dynamics Simulation , PDZ Domains/genetics , PDZ Domains/physiology , Recombinant Fusion Proteins/chemistry , Recombinant Fusion Proteins/genetics , Recombinant Fusion Proteins/metabolism , Tryptophan/chemistry , Tryptophan/genetics
17.
Chemistry ; 27(44): 11279-11284, 2021 Aug 05.
Article in English | MEDLINE | ID: mdl-33830567

ABSTRACT

The enantioselective synthesis of chiral [7]-helical dispirodihydro[2,1-c]indenofluorenes (DSF-IFs) was achieved for the first time in good yields with high er values (er up to 99 : 1). The crucial step of the whole reaction sequence was the enantioselective intramolecular [2+2+2] cycloaddition of tethered triynediols to indenofluorenediols, which was catalyzed by a Rh/SEGPHOS® complex. Further transformations led to the corresponding DSF-IFs. The prepared helically chiral DSF-IFs combine circularly polarized luminescence (CPL) activity (glum =∼10-3 ) with exceptionally high fluorescence quantum yields (up to Φlum =0.97).


Subject(s)
Rhodium , Catalysis , Fluorenes , Luminescence , Stereoisomerism
18.
Protein Sci ; 30(5): 1022-1034, 2021 05.
Article in English | MEDLINE | ID: mdl-33739538

ABSTRACT

The wide variety of protein structures and functions results from the diverse properties of the 20 canonical amino acids. The generally accepted hypothesis is that early protein evolution was associated with enrichment of a primordial alphabet, thereby enabling increased protein catalytic efficiencies and functional diversification. Aromatic amino acids were likely among the last additions to genetic code. The main objective of this study was to test whether enzyme catalysis can occur without the aromatic residues (aromatics) by studying the structure and function of dephospho-CoA kinase (DPCK) following aromatic residue depletion. We designed two variants of a putative DPCK from Aquifex aeolicus by substituting (a) Tyr, Phe and Trp or (b) all aromatics (including His). Their structural characterization indicates that substituting the aromatics does not markedly alter their secondary structures but does significantly loosen their side chain packing and increase their sizes. Both variants still possess ATPase activity, although with 150-300 times lower efficiency in comparison with the wild-type phosphotransferase activity. The transfer of the phosphate group to the dephospho-CoA substrate becomes heavily uncoupled and only the His-containing variant is still able to perform the phosphotransferase reaction. These data support the hypothesis that proteins in the early stages of life could support catalytic activities, albeit with low efficiencies. An observed significant contraction upon ligand binding is likely important for appropriate organization of the active site. Formation of firm hydrophobic cores, which enable the assembly of stably structured active sites, is suggested to provide a selective advantage for adding the aromatic residues.


Subject(s)
Bacterial Proteins/chemistry , Phosphotransferases (Alcohol Group Acceptor)/chemistry , Amino Acid Substitution , Aquifex/enzymology , Aquifex/genetics , Bacterial Proteins/genetics , Catalysis , Catalytic Domain , Mutagenesis, Site-Directed , Phosphotransferases (Alcohol Group Acceptor)/genetics , Protein Structure, Secondary
19.
Langmuir ; 37(8): 2693-2706, 2021 03 02.
Article in English | MEDLINE | ID: mdl-33595317

ABSTRACT

Natural and abundant plant triterpenoids are attractive starting materials for the synthesis of conformationally rigid and chiral building blocks for functional soft materials. Here, we report the rational design of three oleanolic acid-triazole-spermine conjugates, containing either one or two spermine units in the target molecules, using the Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition reaction. The resulting amphiphile-like molecules 2 and 3, bearing just one spermine unit in the respective molecules, self-assemble into highly entangled fibrous networks leading to gelation at a concentration as low as 0.5% in alcoholic solvents. Using step-strain rheological measurements, we show rapid self-recovery (up to 96% of the initial storage modulus) and sol ⇔ gel transition under several cycles. Interestingly, rheological flow curves reveal the thixotropic behavior of the gels. To the best of our knowledge, this kind of behavior was not shown in the literature before, neither for a triterpenoid nor for its derivatives. Conjugate 4, having a bolaamphiphile-like structure, was found to be a nongelator. Our results indicate that the position and number of spermine units alter the gelation properties, gel strength, and their self-assembly behavior. Preliminary cytotoxicity studies of the target compounds 2-4 in four human cancer cell lines suggest that the position and number of spermine units affect the biological activity. Our results also encourage exploring other triterpenoids and their derivatives as sustainable, renewable, and biologically active building blocks for multifunctional soft organic nanomaterials.

20.
Int J Biol Macromol ; 168: 1-12, 2021 Jan 31.
Article in English | MEDLINE | ID: mdl-33290768

ABSTRACT

Constantly increasing attention to bioengineered proteins has led to the rapid development of new functional targets. Here we present the biophysical and functional characteristics of the newly designed CaM/AMBN-Ct fusion protein. The two-domain artificial target consists of calmodulin (CaM) and ameloblastin C-terminus (AMBN-Ct). CaM as a well-characterized calcium ions (Ca2+) binding protein offers plenty of options in terms of Ca2+ detection in biomedicine and biotechnologies. Highly negatively charged AMBN-Ct belongs to intrinsically disordered proteins (IDPs). CaM/AMBN-Ct was designed to open new ways of communication synergies between the domains with potential functional improvement. The character and function of CaM/AMBN-Ct were explored by biophysical and molecular modelling methods. Experimental studies have revealed increased stability and preserved CaM/AMBN-Ct function. The results of molecular dynamic simulations (MDs) outlined different interface patterns between the domains with potential allosteric communication within the fusion.


Subject(s)
Calmodulin/chemistry , Dental Enamel Proteins/chemistry , Amino Acid Sequence/genetics , Binding Sites/physiology , Calcium/chemistry , Dental Enamel Proteins/metabolism , Humans , Intrinsically Disordered Proteins/chemistry , Models, Molecular , Protein Binding/physiology
SELECTION OF CITATIONS
SEARCH DETAIL
...