Monopolar flocking of microtubules in collective motion.

Flocking is a fascinating coordinated behavior of living organisms or self-propelled particles (SPPs). Particularly, monopolar flocking has been attractive due to its potential applications in various fields. However, the underlying mechanism behind flocking and emergence of monopolar motion in flocking of SPPs has remained obscured. Here, we demonstrate monopolar flocking of kinesin-driven microtubules, a self-propelled biomolecular motor system. Microtubules with an intrinsic structural chirality preferentially move towards counter-clockwise direction. At high density, the CCW motion of microtubules facilitates monopolar flocking and formation of a spiral pattern. The monopolar flocking of microtubules is accounted for by a torque generated when the motion of microtubules was obstructed due to collisions. Our results shed light on flocking and emergence of monopolar motion in flocking of chiral active matters. This work will help regulate the polarity in collective motion of SPPs which in turn will widen their applications in nanotechnology, materials science and engineering.

Molecular Epidemiology of HCV RNA Genotype-3 in Dhaka City, Bangladesh.

Hepatitis C virus (HCV) is a causative agent that causes chronic liver diseases worldwide. It is a little, enclosed, single-stranded ribonucleic acid (RNA) virus. The recognition of the pathogenic HCV genotype is critical for the remedy of its sufferers. The aim of this study was to identify the HCV RNA genotype to decide the correct treatment of hepatitis C positive sufferers in Bangladesh. Blood samples were collected from 390 individuals and isolated RNA (60 µg) from blood plasma. Extracted RNA was used for quantitative HCV RNA, and complementary DNA (cDNA) was prepared by polymerase chain reaction (PCR) conducted by reverse transcriptase enzyme. This cDNA amplified in multiplex by RT-PCR, which was performed with specific set of primers. The HCV RNA genotype was detected 297 of 390 patients. Of the 390 test samples, 200 (51.28%) samples were from males and 190 (48.71%) were from females, with age ranging from 5 to 78 years. In all, 166 of 200 male samples and 131/190 female samples were found positive for HCV. Of these 390 participants included in the study, 213 (54.61%) were identified as genotype 3 positive, 78 (20%) as genotype 1 positive, 6 (1.53%) as genotype 6 positive, and the remaining 93 (23.85%) samples were unclassified due to low/undetected viral load. In this study, we detected the highest percentage (30.89%) of genotype 3 HCV in patients aged 51 to 60 years. The results suggested that genotype 3 HCV is frequently present in Bangladesh and it is usually responses better to interferon therapy. However, genotype 1 and 6 HCV have also been found circulating in this country, which demands longer treatments and effective control measures.

Mechanical Deformation of Microtubules on a Two-Dimensional Elastic Medium.

Microtubule, the most rigid filamentous protein in cytoskeleton, plays significant roles in cellular mechano-transduction and mechano-regulation of cellular functions. In cells, the mechanical stress serves as a prevalent stimulus to frequently cause deformation of the microtubules participating in various cellular events. While the experimental and simulation-based approaches have confirmed the role of mechanical stress to tune mechanical properties of microtubule. Yet, the effect of mechanical force on the structural stability and the mechanism of microtubule deformation have remained obscure. Here, we describe the mechanical stress-induced deformation of microtubules using a custom-made mechanical device. We designed the device in a way which allows the microtubules to undergo deformation as response to the applied stress while attached on a two-dimensional elastic substrate through interaction with microtubule-associated motor protein, kinesin. We provide here the method to cause controlled bucking or fragmentation of microtubules by applying compressive or tensile stress on the microtubules, respectively. Such study is crucial to understand the mechanism of deformation in microtubules in cellular environment and their consequences in physiological activities.

Purification of Tubulin from Porcine Brain and its Fluorescence Dye Modification.

Filamentous microtubules, polymers of the heterodimeric protein tubulins play one of the major roles in the emergent nano-biotechnological devices. To develop the feature of those devices, it is important to understand the function of microtubule in in vitro, hence, the availability of purified αß-tubulin is required. Additionally, fluorescently labeled tubulin has become a powerful approach for extensively studying the dynamics of these components. In this chapter, the process of purifying the heterodimeric αß-tubulin from porcine brain will be described, as well as the process of labeling of the purified tubulin with fluorescence dye.