Study Of Biomolecular Interactions Research Articles

Synthesis and structural investigation of o-Vanillin scaffold Schiff base metal complexes: Biomolecular interaction and molecular docking studies

Schiff base metal complexes such as VNPV (VO(IV)), VNPCo (Co(II)), VNPNi (Ni(II)), VNPCu (Cu(II)) and VNPZn (Zn(II)) have been synthesised by using the ligand (VNP) which was prepared by the condensation reaction of o-Vanillin and N-phenyl-o-phenylenediamine. Elemental analysis, UV–visible, FT-IR, ESI-MS, ESR, 1H NMR, XRD, SEM and Cyclic Voltammogram methods were used to evaluate the above metal complexes. The metal center in the complexes is four coordinated by using the tetradentate N2O2 donar Schiff base ligand to form square pyramidal geometry for VO(IV) metal complex and square planar geometry for other metal complexes. The disc well-diffusion method was used on agar plate to assess the in vitro antibacterial activities of the ligand and its metal complexes against bacteria such B. amyloliquefaciens, B. cereus, B. subtilis, S. epidermidis and S. aureus. From the results demonstrate that the metal complexes of the ligand exhibit better antibacterial behaviour on S. aureus bacteria than the other bacterial strains. The antioxidant studies were carried by DPPH free radical scavenging assay method and from the results it is found that the VNPCu complex has better antioxidant activity than the ligand and other metal complexes. Additionally, the spectral techniques like UV–visible absorption, fluorescence and molecular docking methods were used to examine the interactions between the ligand and metal complexes with biomolecules (DNA and BSA). The CT-DNA cleavage activities of metal complexes with CT DNA were examined by gelelectrophoretic method. From the results, the VNPCu complex has only cleave the DNA molecules than the other metal complexes. According to the results of the investigations, the metal complex VNPCu exhibits better interaction with the biomolecules than the free ligand and other metal complexes.

Quantifying Biomolecular Interactions Using Slow Mixing Mode (SLOMO) Nanoflow ESI-MS.

Electrospray ionization mass spectrometry (ESI-MS) is a powerful label-free assay for detecting noncovalent biomolecular complexes in vitro and is increasingly used to quantify binding thermochemistry. A common assumption made in ESI-MS affinity measurements is that the relative ion signals of free and bound species quantitatively reflect their relative concentrations in solution. However, this is valid only when the interacting species and their complexes have similar ESI-MS response factors (RFs). For many biomolecular complexes, such as protein–protein interactions, this condition is not satisfied. Existing strategies to correct for nonuniform RFs are generally incompatible with static nanoflow ESI (nanoESI) sources, which are typically used for biomolecular interaction studies, thereby significantly limiting the utility of ESI-MS. Here, we introduce slow mixing mode (SLOMO) nanoESI-MS, a direct technique that allows both the RF and affinity (Kd) for a biomolecular interaction to be determined from a single measurement using static nanoESI. The approach relies on the continuous monitoring of interacting species and their complexes under nonhomogeneous solution conditions. Changes in ion signals of free and bound species as the system approaches or moves away from a steady-state condition allow the relative RFs of the free and bound species to be determined. Combining the relative RF and the relative abundances measured under equilibrium conditions enables the Kd to be calculated. The reliability of SLOMO and its ease of use is demonstrated through affinity measurements performed on peptide–antibiotic, protease–protein inhibitor, and protein oligomerization systems. Finally, affinities measured for the binding of human and bacterial lectins to a nanobody, a viral glycoprotein, and glycolipids displayed within a model membrane highlight the tremendous power and versatility of SLOMO for accurately quantifying a wide range of biomolecular interactions important to human health and disease.

Synthesis, characterization, biomolecular interaction and in vitro glucose metabolism studies of dioxidovanadium(V) benzimidazole compounds

We have previously reported that the metal-based anti-diabetic drug candidates, cis-[VO2(obz)py] (1) (Hobz = 2-hydroxyphenyl-1H-benzimidazole and py = pyridine) and cis-[VO2(Hpybz)(pybz)] (2) (Hpybz = 2-pyridyl-1H-benzimidazole) illustrated hypoglycaemic activities both in vitro and in vivo, respectively. Herein, we report the biomolecular interaction studies of 1 and 2 as well as their new analogues: cis-[VO2(Hmpybz)(mpybz)] (3) (Hmpybz = 2-(4-methyl-2-pyridyl-1H-benzimidazole) and cis-[VO2(mobz)py] (4) (Hombz = 2-(5–6 dimethyl-2-pyridine)-1H-benzimidazole) towards Bovine Serum Albumin (BSA) and Protein Phosphatase Tyrosine (PTP)-1B enzyme, respectively. The new metal complexes 3 and 4 were characterized with the aid of various characterization techniques and their structures were confirmed by single crystal X-ray crystallography and elemental analysis. Unique concentration-dependent PTP-1B inhibitory activities of 2 and 3 were observed under pre- and post-lysis experimental conditions. Lactate assays showed that 2 and 3 reduces the rate of lactate production. As there is a linear relationship between lactate levels and insulin resistance, this suggests that compounds 2 and 3 are able to alleviate this phenotype via the reduction of lactate build-up in HEK293T cells. The glucose consumption rate was insignificantly altered in response to 2 and 3, suggesting that these compounds do not affect glucose uptake in HEK293T cells.

Synthetic approach toward spiro quinoxaline-β-lactam based heterocyclic compounds: Spectral characterization, SAR, pharmacokinetic and biomolecular interaction studies

Series of spiro quinoxaline-β-lactam based heterocyclic compounds (QL 1 – QL 21) were synthesized and characterized by spectroscopic techniques like 1H-NMR, LC-MS, FT-IR spectroscopy and elemental analysis. The binding mode and binding strength between compounds and calf thymus-DNA were estimated by UV–visible spectroscopy, viscosity measurement and molecular docking studies. The compounds bind with the DNA through partial intercalation mode. In the absorption titration experiment, the K b values for all the synthesized compounds were found in the range of 0.24–0.64 × 105 M−1. The protein binding studies of all the synthesized compounds were evaluated by absorption titration experiment, and the K b value for all the compounds was obtained in the range of 0.030–1.571 × 104 M−1. The compounds were screened against two Gram (+ve) and three Gram (–ve) bacteria for antimicrobial activity. The MIC values for all the synthesized compounds were found in 95–255 µM. The LC50 values (cytotoxicity) of the synthesized compounds (QL 1–QL 21) were found in the range of 4.00–12.89 µg/mL. The ADME study was carried out using the online platform SwissADME and admetSAR to evaluate the pharmacokinetic profile of all the synthesized compounds. All the compounds were screened for anticancer activity against the human osteosarcoma (MG-63) cell line. The result shows that all the compounds exhibit effective anticancer activity. Communicated by Ramaswamy H. Sarma

ROS -mediated anticancer response of potent copper(II) drug entities derived from S, O and N, N chelating donor scaffold: Single X-ray crystal diffraction and spectroscopic studies

New Cu(II) anticancer drug entities derived from S, O, and N, N donor chelating scaffolds were synthesized and thoroughly characterized by various spectroscopic and single X-ray diffraction studies. The single X-ray crystal structure of 1 and 2 revealed a monoclinic and triclinic crystal system with space group C 2 / c and P -1, respectively. The biomolecular interaction studies of 1 and 2 with ct-DNA were carried out by employing a battery of biophysical techniques, viz., absorption, emission, circular dichroic, and electrochemical (CV) and corroborative results of these experiments demonstrated avid electrostatic binding via surface groove. The synthesized Cu(II) complexes showed high efficacy as ROS generators involving Cu(II)/Cu(I) redox-active pair as evidenced by cleavage assay in the presence of radical scavengers. The ROS generation in the presence of copper-based complexes is considered one of the most favorable cell death mechanisms for the inhibition of cancers. In vitro anticancer activity of 1 and 2 was, therefore, evaluated against a panel of five human cancer cell lines, namely MCF-7, MDA-MB-231, Hop-62, AW1356, and SiHa, and results of cytotoxicity demonstrated good anticancer response against all tested cancerous strains with GI50 value <10 µM, except by 1 against MDA-MB-231, Hop-62 and AW1356 cell lines. Interestingly, 2 has displayed considerable cytotoxicity against MCF-7, Hop-62, and SiHa cancer cell lines even better than that of standard drug adriamycin. Furthermore, computational DFT studies validated the high binding efficacy and significant cytotoxicity of complex 2, which could be attributed to high positive charge density over the Cu(II) center.

Structured surface wetting of a PTFE flow-cell for terahertz spectroscopy of proteins

We have fabricated a terahertz compatible polytetrafluoroethylene (PTFE) based microfluidic flow-cell, in which terahertz time-domain spectroscopy of a range of concentrations of aqueous bovine serum albumin (BSA) was performed, demonstrating the device’s suitability for future studies of biomolecular interactions. The novel combination of oxygen plasma treatments and milling was used to both increase and decrease the wettability of the channel and surrounding substrate (to superhydrophobic levels) respectively, producing a stark contrast in contact angles allowing surface tension effects to confine liquid in the channel. PTFE is a chemically inert, bio-compatible material with ideal spectroscopic properties at sub-millimetre wavelengths.

Label-free Quantification of Direct Protein-protein Interactions with Backscattering Interferometry.

The functional performance of a cell depends on how macromolecules, in particular proteins, come together in a precise orientation, how they assemble into protein complexes and interact with each other. In order to study protein-protein interactions at a molecular level, a variety of methods to investigate these binding processes yield affinity constants and/or the identification of binding regions. There are several well-established biophysical techniques for biomolecular interaction studies, such as fluorescence spectroscopy and surface plasmon resonance. Although these techniques have been proven to be efficient, they either need labeling or immobilization of one interaction partner. Backscattering interferometry (BSI) is a label-free detection method, which allows label- and immobilization-free interaction analysis under physiologically relevant conditions with high sensitivity and in small volumes. We used BSI to measure the interaction of the neuronal calcium sensor recoverin with its target G protein-coupled receptor kinase 1 (GRK1) as a model system. Increasing concentrations of purified recoverin were mixed with a specific concentration of a GRK1 fusion protein. In this protocol, we provide a full description of the instrumental setup, data acquisition, and evaluation. Equilibrium dissociation constants of recoverin-GRK1 interaction determined by the BSI instrumental setup are in full agreement with affinity constants obtained by different methods as described in the literature.

In vitro biomolecular interaction studies and cytotoxic activities of copper(II) and zinc(II) complexes bearing ONS donor thiosemicarbazones

Among all the bio‐metals, zinc and copper derivatives of ONS donor thiosemicarbazone have aroused great interest because of their potential biological applications. Multisubstituted thiosemicarbazone ligand H2dspt (3,5‐dichlorosalicylaldehyde‐N4‐phenylthiosemicarbazone) derived new ternary complexes like [Zn(dspt)(phen)]‧DMF (1) and [Cu(dspt)(phen)]‧DMF (2), and another thiosemicarbazone, H2dsct (3,5‐dichlorosalicylaldehyde‐N4‐cyclohexylthiosemicarbazone), derived [Cu(dsct)(bipy)]‧DMF (3). These complexes have been characterized by elemental analysis (CHNS), Fourier transform infrared (FT‐IR), ultraviolet–visible (UV–Vis) and proton nuclear magnetic resonance (1H‐NMR) spectra. The structures of the complexes were obtained by single‐crystal X‐ray diffraction analysis. Compounds1and2got crystallized in the monoclinicP21/cspace group. The complexes showed interesting supramolecular interaction, which in turn stabilizes the complexes. The ground state electronic configurations of the complexes were studied using the B3LYP/LANL2DZ basis set, and ESP plots of complexes were investigated. The interaction of the complexes with calf thymus DNA (CT‐DNA) was studied using absorption and fluorescence spectroscopic methods. A UV study of the interaction of the complexes with calf thymus DNA (CT‐DNA) has shown that the complexes can effectively bind to CT‐DNA, and [Cu(dspt)(phen)]·DMF (2) exhibited the highest binding constant to CT‐DNA (Kb= 3.7 × 104). Fluorescence spectral studies also indicated that Complex2binds relatively stronger with CT DNA through intercalative mode, exhibiting higher binding constant (Kq= 4.7 × 105). The DNA cleavage result showed that the complexes are capable of cleaving the DNA without the help of any external agent. Molecular docking studies were carried out to understand the binding of complexes with the molecular target DNA. Complex2exhibited the highest cytotoxicity against human breast cancer cell line MD‐MBA‐231 (IC50= 23.93 μg/mL) as compared to Complex1(IC50= 44.40 μg/mL).

Alkynylselenium-functionalized benzothiadiazoles: Synthesis, photophysics, electrochemistry, and biomolecular interaction studies

We describe herein our results on the synthesis of 4,7-bis((arylselanyl)ethynyl)benzo[c][1,2,5]thiadiazoles 3 by the silver-catalyzed direct selanylation of 4,7-diethynylbenzo[c][1,2,5]thiadiazole 1 with diaryl diselenides. Three new compounds were obtained in good yields using 10 mol% of AgNO3 as a catalyst under mild reaction conditions. In addition, the preliminary investigation of photophysical properties of the alkynyl derivatives by UV–Vis and steady-state emission fluorescence and electrochemical behavior was also presented. The photophysical properties of the new compounds were determined and experimental and theoretical DNA/HSA binding properties were assessed.

Study of Biomolecular Interactions of Mitochondrial Proteins Related to Alzheimer's Disease: Toward Multi-Interaction Biomolecular Processes.

Progressive mitochondrial dysfunction due to the accumulation of amyloid beta (Aβ) peptide within the mitochondrial matrix represents one of the key characteristics of Alzheimer’s disease (AD) and appears already in its early stages. Inside the mitochondria, Aβ interacts with a number of biomolecules, including cyclophilin D (cypD) and 17β-hydroxysteroid dehydrogenase type 10 (17β-HSD10), and affects their physiological functions. However, despite intensive ongoing research, the exact mechanisms through which Aβ impairs mitochondrial functions remain to be explained. In this work, we studied the interactions of Aβ with cypD and 17β-HSD10 in vitro using the surface plasmon resonance (SPR) method and determined the kinetic parameters (association and dissociation rates) of these interactions. This is the first work which determines all these parameters under the same conditions, thus, enabling direct comparison of relative affinities of Aβ to its mitochondrial binding partners. Moreover, we used the determined characteristics of the individual interactions to simulate the concurrent interactions of Aβ with cypD and 17β-HSD10 in different model situations associated with the progression of AD. This study not only advances the understanding of Aβ-induced processes in mitochondria during AD, but it also provides a new perspective on research into complex multi-interaction biomolecular processes in general.

Synthesis, characterization, structural-activity relationship and biomolecular interaction studies of heteroleptic Pd(II) complexes with acetyl pyridine scaffold

A series of substituted hydrazinyl pyridine based Schiff base ligands (L1–L6) and corresponding palladium(II) complexes were synthesized and characterized by conductivity measurement, 1H NMR, 13C NMR and liquid chromatography mass spectrometry (LC-MS). Synthesized compounds were screened against various biological activities. UV–Vis spectroscopy, fluorescence spectroscopy, viscosity measurement, and molecular docking studies were used to determine the binding mode between complexes and HS-DNA, which suggest intercalation mode of DNA binding. The protein binding study of complexes was evaluated by UV–visible spectroscopy. Antibacterial activity of the complexes was screened against two Gram (+ve) and three Gram (−ve) bacteria and the result shows that all complexes are more effective against microorganisms than their respective ligands. The cytotoxicity of the synthesized compounds was tested against brine shrimp and S. pombe cell. The LC50 values of the ligand and complexes are found in the range of 9.24–14.12 μg/mL and 5.68–7.94 μg/mL, respectively. The DNA cleavage activity of metal complexes was performed using agarose gel electrophoresis. All compounds were tested for anticancer activity against human colorectal (HCT-116) cancer cell lines. The result shows that all the compounds exhibited effective cytotoxicity against the tested cell line.

Physicochemical, in-vitro therapeutic activity and biomolecular interaction studies of Mn(II), Ni(II) and Cu(II) complexes tethered with O2N2 ligand backbone.

Two major health crisis of today's world are antimicrobial drug resistance and type II diabetes. To tackle them, there is an immediate requirement for the development of new and safer drugs and the present work is one such quest for novel and efficient drug candidates. We have developed three trace metal coordination compounds tethered with a reduced salen ligand {H2(hpdbal)2-an} (L), namely, a manganese-salan complex, [MnII(H2O)2{(hpdbal)2-an}] (1), a nickel-salan complex, [NiII{(hpdbal)2-an}] (2) and a copper-salan complex, [CuII{(hpdbal)2-an}] (3). The compounds were characterized by elemental analysis, vibrational spectroscopy, electronic spectroscopy, thermogravimetric analysis, nuclear magnetic resonance and electron-paramagnetic resonance techniques. The compounds were evaluated for antimicrobial activity against seven pathogens (Escherichia coli, Klebsiella pneumonia, Acinetobacter baumannii, Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans and Cryptococcus neoformans) and antidiabetic activity by mimicking diabetic environment on the immortal human liver cancer cells, HepG2. Complexes 1 and 2 were additionally tested for their reactivity and stability in biological media mimic conditions. The nickel(II) salan complex (2) exhibited noteworthy antifungal activity against Candida albicans and the manganese(II) salan complex (1) induced increased glucose uptake by the insulin resistant cells. Both compounds were found to be stable when solution pH conditions were varied from 3 to 9. They exhibited strong affinity of binding towards a carrier protein, bovine serum albumin which was evaluated with the aid of multi-spectroscopic techniques.

TCSPC Camera for Real Time Video Rate FLIM Acquisition Based on CMOS Technology

The use of fluorescence lifetime imaging microscopy (FLIM) is appealing for the study of biomolecular interactions. Traditionally FLIM has made use of scanning techniques to image a sample with a “single-pixel” detector, while widefield approaches have mainly related to intensity-based imaging. The latter is is advantageous to study mobile samples or kinetics, usually not achievable with FLIM. Rapid fluorescence lifetime imaging is especially important in the monitoring of biological samples, eg.

Phage Display in the Quest for New Selective Recognition Elements for Biosensors.

Phages are bacterial viruses that have gained a significant role in biotechnology owing to their widely studied biology and many advantageous characteristics. Perhaps the best-known application of phages is phage display that refers to the expression of foreign peptides or proteins outside the phage virion as a fusion with one of the phage coat proteins. In 2018, one half of the Nobel prize in chemistry was awarded jointly to George P. Smith and Sir Gregory P. Winter “for the phage display of peptides and antibodies.” The outstanding technology has evolved and developed considerably since its first description in 1985, and today phage display is commonly used in a wide variety of disciplines, including drug discovery, enzyme optimization, biomolecular interaction studies, as well as biosensor development. A cornerstone of all biosensors, regardless of the sensor platform or transduction scheme used, is a sensitive and selective bioreceptor, or a recognition element, that can provide specific binding to the target analyte. Many environmentally or pharmacologically interesting target analytes might not have naturally appropriate binding partners for biosensor development, but phage display can facilitate the production of novel receptors beyond known biomolecular interactions, or against toxic or nonimmunogenic targets, making the technology a valuable tool in the quest of new recognition elements for biosensor development.

A Universal Photochemical Method to Prepare Carbohydrate Sensors Based on Perfluorophenylazide Modified Polydopamine for Study of Carbohydrate-Lectin Interactions by QCM Biosensor.

A universal photochemical method to prepare carbohydrate sensors based on perfluorophenylazide (PFPA) modified polydopamine (PDA) for the study of carbohydrate–lectin interactions by a quartz crystal microbalance (QCM) biosensor was developed. The PFPA was immobilized on PDA-coated gold sensors via Schiff base reactions. Upon light irradiation, the underivatized carbohydrates were inserted into the sensor surface, including mannose, galactose, fucose and N-acetylglucosamine (GlcNAc). Carbohydrate sensors were evaluated for the binding to a series of plant lectins. A kinetic study of the interactions between mannose and concanavalin A (Con A), fucose and Ulex europaeus agglutinin I (UEA-I) were performed. This method can eliminate the tedious modification of carbohydrates, improve the experimental efficiency, and reduce the experimental cost, which is of great significance for the development of QCM biosensors and the study of biomolecular interactions.

Superresolution microscopy with novel BODIPY-based fluorophores.

Multicolor single-molecule localization microscopy (SMLM) expands our understanding of subcellular details and enables the study of biomolecular interactions through precise visualization of multiple molecules in a single sample with resolution of ~10–20 nm. Probe selection is vital to multicolor SMLM, as the fluorophores must not only exhibit minimal spectral crosstalk, but also be compatible with the same photochemical conditions that promote fluorophore photoswitching. While there are numerous commercially available photoswitchable fluorophores that are optimally excited in the standard Cy3 channel, they are restricted to short Stokes shifts (<30 nm), limiting the number of colors that can be resolved in a single sample. Furthermore, while imaging buffers have been thoroughly examined for commonly used fluorophore scaffolds including cyanine, rhodamine, and oxazine, optimal conditions have not been found for the BODIPY scaffold, precluding its routine use for multicolor SMLM. Herein, we screened common imaging buffer conditions including seven redox reagents with five additives, resulting in 35 overall imaging buffer conditions to identify compatible combinations for BODIPY-based fluorophores. We then demonstrated that novel, photoswitchable BODIPY-based fluorophores with varied length Stokes shifts provide additional color options for SMLM using a combination of BODIPY-based and commercially available photoswitchable fluorophores.

Opto-Thermophoretic Attraction, Trapping, and Dynamic Manipulation of Lipid Vesicles.

Lipid vesicles are important biological assemblies, which are critical to biological transport processes, and vesicles prepared in the lab are a workhorse for studies of drug delivery, protein unfolding, biomolecular interactions, compartmentalized chemistry, and stimuli-responsive sensing. The current method of using optical tweezers for holding lipid vesicles in place for single-vesicle studies suffers from limitations such as high optical power, rigorous optics, and small difference in the refractive indices of vesicles and water. Herein, we report the use of plasmonic heating to trap vesicles in a temperature gradient, allowing long-range attraction, parallel trapping, and dynamic manipulation. The capabilities and limitations with respect to thermal effects on vesicle structure and optical spectroscopy are discussed. This simple approach allows vesicle manipulation using down to 3 orders of magnitude lower optical power and at least an order of magnitude higher trapping stiffness per unit power than traditional optical tweezers while using a simple optical setup. In addition to the benefit provided by the relaxation of these technical constraints, this technique can complement optical tweezers to allow detailed studies on thermophoresis of optically trapped vesicles and effects of locally generated thermal gradients on the physical properties of lipid vesicles. Finally, the technique itself and the large-scale collection of vesicles have huge potential for future studies of vesicles relevant to detection of exosomes, lipid-raft formation, and other areas relevant to the life sciences.

A novel silver (I) complex of α-keto phosphorus ylide: Synthesis, characterization, crystal structure, biomolecular interaction studies, molecular docking and in vitro cytotoxic evaluation

{[Ag(FBPY)2]+(FBPYH)+}(OTF)2, FBPY=FPhC(O)C(H)PPh3, FBPYH =FC6H4COCH2PPh3, OTF=CF3SO3, a ylidic complex, was prepared through the reaction of silver trifluoromethanesulfonate (AgOTf) and ylide [FBPY] in 1:2 M ratio and characterized using various techniques. X-ray crystallography was used to determine the crystal structure. CT-DNA binding interaction of the synthesis compound was tested by fluorescence spectroscopy, UV–Vis absorption spectroscopy, and viscometric titration method. The data by the analysis revealed that the Ag complex could bind to DNA through the groove binding mode. The emission titration of bovine serum albumin (BSA) with the complex showed a static process for the fluorescence quenching mechanism of BSA. In addition, the donor (BSA) - acceptor (Ag complex) distance was calculated by using fluorescence resonance energy transfer (FRET). The results of competitive binding by means of Warfarin, Ibuprofen and Digoxin site markers revealed that the complex was bound to the site I of BSA. Notably, molecular docking studies were used for the determination of DNA and BSA-Ag (I) complex binding. Finally, it was shown that the complex had remarkable in vitro cytotoxicity against melanoma (B16F0) and colon carcinoma (C26) cancer cell lines, as shown by the use of MTT([3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide] colorimetric assay.

Nuclear magnetic resonance structure-based drug design.

Nuclear magnetic resonance structure-based drug design.

Cover Picture: MicroRNA‐Directed Intracellular Self‐Assembly of Chiral Nanorod Dimers (Angew. Chem. Int. Ed. 33/2018)

The chiral self-assembly of plasmonic nanorod dimers in living cells, driven by complementary binding to a target miRNA sequence, and leading to specific plasmonic circular dichroism, surface-enhanced Raman scattering (SERS), and fluorescence signals is described in the Communication by H. Kuang, L. M. Liz-Marzán et al. on page 10544 ff. The method allows in situ imaging as well as highly sensitive and selective miRNA detection. It can also be extended to the study of biomolecular interactions, trafficking, and kinetics inside single living cells. The chiral self-assembly of plasmonic nanorod dimers in living cells, driven by complementary binding to a target miRNA sequence, and leading to specific plasmonic circular dichroism, surface-enhanced Raman scattering (SERS), and fluorescence signals is described in the Communication by H. Kuang, L. M. Liz-Marzán et al. on page 10544 ff. The method allows in situ imaging as well as highly sensitive and selective miRNA detection. It can also be extended to the study of biomolecular interactions, trafficking, and kinetics inside single living cells. Molecular Knots Kinetic Resolution DNA Nanotechnology