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Scanning Electrochemical Microscopy of Living Cells
Published in Allen J. Bard, Michael V. Mirkin, Scanning Electrochemical Microscopy, 2022
Changyue Du, Thilini Suduwella, Isabelle Beaulieu, Steen B. Schougaard, Janine Mauzeroll
Twelve years later, Guo and Amemiya61 studied the local permeability of the nuclear envelope from Xenopus laevis oocytes using feedback mode SECM. Based on the approach curves, it was established that the transport of redox molecules across the nuclear envelope membrane was diffusion limited. Chronoamperometry performed inside the nucleus suggested that the concentration and diffusion coefficient of the redox mediator was diminished in the intracellular environment. From fits of the experimental approach curves to theory, it was determined that the nuclear envelope membrane was more permeable than conventional bilayer lipid membranes. This enhancement in permeability was facilitated by the nuclear pore complex, which mediated molecular transport between the cytoplasm and the nucleus. Using a combination of electrochemical and fluorescence techniques, the flux through, the channel dimensions and transport function of the nuclear pore complex were further investigated. Interestingly, this study corroborated existing glass pipette and hourglass techniques that proposed that most nuclear pore complexes on the nucleus are open.
General Introductory Topics
Published in Vadim Backman, Adam Wax, Hao F. Zhang, A Laboratory Manual in Biophotonics, 2018
Vadim Backman, Adam Wax, Hao F. Zhang
The nuclear pores are large (about 100 nm in diameter) and serve to facilitate the exchange of materials between the nucleus and the cytoplasm. This exchange is a critically important process as a part of gene expression, as we will soon see. The exchanged molecules include various transcription factors going into the nucleus to regulate gene transcription and messenger RNA (mRNA) getting out of the nucleus to be read by the ribosomes in the cytoplasm as part of the translation process leading to protein synthesis. These processes are discussed later in more detail. The number of nuclear pores correlates with the metabolic activity of a cell. A metabolically silent cell may have as few as dozens of pores, whereas an active cell may have as many as thousands. Another function of nuclear pores is that they fuse the outer and the inner nuclear membranes; indeed, nuclear pores are not simple “holes” in the envelope but rather protein complexes called nucleoporins. Yet another function of the pores is active transport. Although small molecules freely diffuse through the pores, larger molecules are recognized by specific sequences, and their diffusion is assisted with the help of nucleoporins, which is known as the RAs-related nuclear protein cycle or RAN cycle.
Naturally Occurring Polymers—Animals
Published in Charles E. Carraher, Carraher's Polymer Chemistry, 2017
While DNA is the depository of our genetic information, it is “held captive” or “protected” by the nuclear envelope, remaining within this envelope. Yet, the information held by the double-stranded DNA is transferred throughout the cell with results felt throughout the body. Briefly, polymerase transcribes the information on the DNA into single-stranded mRNA. The mRNA single strands move from the cell nucleus into the cell cytoplasm through openings in the nuclear envelope called nuclear pore complexes.
Nonviral gene delivery using PAMAM dendrimer conjugated with the nuclear localization signal peptide derived from human papillomavirus type 11 E2 protein
Published in Journal of Biomaterials Science, Polymer Edition, 2021
Jeil Lee, Yong-Eun Kwon, Jaegi Kim, Dong Woon Kim, Hwanuk Guim, Jehyeong Yeon, Jin-Cheol Kim, Joon Sig Choi
Therapeutic genes must be delivered to the nuclear region for successful gene therapy. However, nonviral vectors have difficulties in selectively delivering DNA molecules into the nuclear region, limiting their application in genetic medicine. Nonviral gene delivery is inhibited by membranous barriers; one of these, the nuclear envelope, consists of two lipid bilayer membranes and a nuclear pore complex (NPC), limiting the entry of molecules larger than 9 nm. NLS is a tag sequence that enables the transport of proteins from the cytoplasm to the nuclear region and permits the active transport of molecules up to 39 nm [29]. Since the size of the cationic polymer/pCN-Luci polyplexes was too large to directly penetrate the NPC pores, we hypothesized that PAMAM derivatives conjugated with NLS peptides/pCN-Luci polyplexes would be localized in the perinuclear region because of their size, and subsequently delivered to the nuclear region when the nuclear envelope disappears during mitosis. In our previous study, polyplexes of PAMAM derivatives conjugated with NLS peptides and pCN-Luci showed high transfection efficiency and perinuclear localization. A series of experiments and previous findings indicate that each factor, such as enhanced cellular uptake and proton-buffering capacity, affects the transfection efficiency of PAMAM derivatives modified with NLS peptides, which showed a lower proton-buffering capacity than PEI 25 kDa [17–19]. If proton-buffering capacity was the main reason for the increased transfection efficiency, PAMAM derivatives modified with NLS peptides should have a buffering capacity similar to that of PEI (25 kDa). Therefore, the improved transfection efficiency of RKRAR- and RKRARH-PAMAM G2 may be a product of the combined effects of these three factors.