A single-molecule analysis reveals morphological targets for cellulase synergy.

The mechanisms of enzyme activity on solid substrates are not well understood. Unlike enzyme catalysis in aqueous solutions, enzyme activity on surfaces is complicated by adsorption steps and structural heterogeneities that make enzyme-substrate interactions difficult to characterize. Cellulase enzymes, which catalyze the depolymerization of cellulose, show binding specificities for different cellulose surface morphologies, but the influence of these specificities on the activity of multienzyme mixtures has remained unclear. We developed a metric to quantify binding-target arrangements determined by photoactivated localization microscopy, and we used that metric to show that combinations of cellulases designed to bind within similar but nonidentical morphologies can have synergistic activity. This phenomenon cannot be explained with the binary crystalline or amorphous classifications commonly used to characterize cellulase-binding targets. Our results reveal a strategy for improving the activity of cellulolytic mixtures and demonstrate a versatile method for investigating protein organization on heterogeneous surfaces.

Million spot binding array platform for exploring and optimizing multiple simultaneous detection events.

Large-scale, high-throughput specificity assays to characterize binding properties within a competitive and complex environment of potential binder-target pairs remain challenging and cost prohibitive. Barcode cycle sequencing (BCS) is a molecular binding assay for proteins, peptides, and other small molecules that is built on a next-generation sequencing (NGS) chip. BCS uses a binder library and targets labeled with unique DNA barcodes. Upon binding, binder barcodes are ligated to target barcodes and sequenced to identify encoded binding events. For complete details on the use and execution of this protocol, please refer to Hong et al. (2022).

ProtSeq: Toward high-throughput, single-molecule protein sequencing via amino acid conversion into DNA barcodes.

We demonstrate early progress toward constructing a high-throughput, single-molecule protein sequencing technology utilizing barcoded DNA aptamers (binders) to recognize terminal amino acids of peptides (targets) tethered on a next-generation sequencing chip. DNA binders deposit unique, amino acid-identifying barcodes on the chip. The end goal is that, over multiple binding cycles, a sequential chain of DNA barcodes will identify the amino acid sequence of a peptide. Toward this, we demonstrate successful target identification with two sets of target-binder pairs: DNA-DNA and Peptide-Protein. For DNA-DNA binding, we show assembly and sequencing of DNA barcodes over six consecutive binding cycles. Intriguingly, our computational simulation predicts that a small set of semi-selective DNA binders offers significant coverage of the human proteome. Toward this end, we introduce a binder discovery pipeline that ultimately could merge with the chip assay into a technology called ProtSeq, for future high-throughput, single-molecule protein sequencing.

Optical detection and grading of lung neoplasia by Raman microspectroscopy.

The aim of this study was to investigate whether Raman spectroscopy could be used to identify and potentially grade lung neoplasia in cell samples. Normal human bronchial epithelial cells (HBEpCs) were analyzed by Raman spectroscopy and compared with (i) HBEpCs expressing human papillomavirus (HPV) type 16 E7 or CDK4; (ii) the immortalized bronchial epithelial cell line BEP2D and (iii) its asbestos-transformed derivative AsbTB2A. Overall, Raman spectroscopy, in combination with a linear discriminant analysis algorithm, was able to identify abnormal cells with a sensitivity of 91% and a specificity of 75%. Subdivision of the cell types into 3 groups, representing normal cells (HBEpCs), cells with extended lifespan (HBEpCs expressing HPV 16 E7 or CDK4) and immortalized/transformed cells (BEP2D and AsbTB2A) showed that Raman spectroscopy identifies cells in these categories correctly with sensitivities of 75, 79 and 87%, and specificities of 91, 85 and 96%, respectively. In conclusion, Raman spectroscopy can, with high sensitivity, detect the presence of neoplastic development in lung cells and identify the stage of this development accurately, suggesting that this minimally invasive optical technology has potential for lung cancer diagnosis.

Control of protein function through optochemical translocation.

Controlled manipulation of proteins and their function is important in almost all biological disciplines. Here, we demonstrate control of protein activity with light. We present two different applications-light-triggered transcription and light-triggered protease cleavage-both based on the same concept of protein mislocation, followed by optochemically triggered translocation to an active cellular compartment. In our approach, we genetically encode a photocaged lysine into the nuclear localization signal (NLS) of the transcription factor SATB1. This blocks nuclear import of the protein until illumination induces caging group removal and release of the protein into the nucleus. In the first application, prepending this NLS to the transcription factor FOXO3 allows us to optochemically switch on its transcription activity. The second application uses the developed light-activated NLS to control nuclear import of TEV protease and subsequent cleavage of nuclear proteins containing TEV cleavage sites. The small size of the light-controlled NLS (only 20 amino acids) minimizes impact of its insertion on protein function and promises a general approach to a wide range of optochemical applications. Since the light-activated NLS is genetically encoded and optically triggered, it will prove useful to address a variety of problems requiring spatial and temporal control of protein function, for example, in stem-cell, developmental, and cancer biology.

Nanoshells for surface-enhanced Raman spectroscopy in eukaryotic cells: cellular response and sensor development.

The application of gold nanoshells (NS) as a surface-enhanced Raman (SER) platform for intracellular sensing in NIH-3T3 fibroblast cells was studied by using a near-infrared Raman system. To show the feasibility of using these 151 +/- 5 nm sized solution-stable nanoparticles inside living cells, we investigated the uptake, cellular response, and the health of the cell population. We show that NS are taken up voluntarily and can be found in the cytosol by transmission electron microscopy (TEM), which also provides detailed information about location and immediate surrounding of the NS. The internalization into cells has been found to be independent of active cellular mechanisms, such as endocytosis, and can be suggested to be of passive nature. Uptake of NS into cells can be controlled, and cells show no increase in necrosis or apoptosis as a result; we show that NS-based intracytosolic SER spectra can be measured on biological samples using short acquisition times and low laser powers. We demonstrate its application using 4-mercaptobenzoic acid (4-MBA)-functionalized nanoshells as a pH sensor.