Atomic Force Microscopy of Biopolymers on Graphite Surfaces

Myeloperoxidase‐induced fibrinogen unfolding and clotting

“…Retaining of the secondary structure in fibrinogen–myeloperoxidase clots resulted from CD spectra (Figure 1c) allows interpreting myeloperoxidase‐induced fibrinogen unfolding as partial loss of fibrinogen tertiary rather than secondary structure. Similar unfolding of fibrinogen conformation has been observed after several minutes of fibrinogen adsorption on a GM‐HOPG surface (Barinov, Protopopova, et al, 2018; Dubrovin et al, 2019). However, in the present work the contribution of surface‐induced unfolding of fibrinogen molecules is negligible due to relatively small time of adsorption (5 s; Barinov et al, 2016; Barinov, Protopopova, et al, 2018; Dubrovin et al, 2019; Protopopova et al, 2015).…”

“…For AFM investigations we have used a GM‐HOPG surface as a substrate, which was shown to improve AFM‐based structural analysis of single protein molecules, in particular fibrinogen, as compared with other conventional AFM substrates including mica (Dubrovin & Klinov, 2021; Klinov et al, 2020; Protopopova et al, 2015). Fibrinogen molecules adsorbed onto a GM‐HOPG surface for 5 s are characterized by a trinodular structure with two outer globular regions 3–3.5 nm high and one central globular region ~2 nm high (Barinov et al, 2016; Dubrovin et al, 2019; Protopopova et al, 2015). Myeloperoxidase molecules deposited by the same procedure adsorb onto a GM‐HOPG surface as globular structures ~4 nm high (Barinov, Vlasova, et al, 2018).…”

“…For AFM investigations 0.5 μl of protein mixture (fibrinogen–myeloperoxidase, fibrinogen–ferritin, fibrinogen–thrombin or fibrinogen–myeloperoxidase–thrombin) prepared as described above was deposited onto a GM‐HOPG surface for 5 s. Short deposition time allows to minimize the contamination of the sample from the impurities and avoid surface‐induced unfolding of fibrinogen (Barinov, Protopopova, et al, 2018; Dubrovin et al, 2019). After that, 100 μl of water was added on the surface (rinsing) followed by immediate removal of the whole droplet by a nitrogen flow.…”

Visualization of G-Quadruplexes, i-Motifs and Their Associates

“…Модификация поверхности ВОПГ GM, проводимая обычно с помощью дропкастинга, приводит к формированию однородного, самоупорядоченного слоя этих молекул толщиной меньше 1 нм [80,81]. Как и в случае модификации пентиламином, аминогруппы GM делают возможным адсорбцию отдельных молекул ДНК на поверхность и их дальнейшее исследование с помощью АСМ [82].…”

“…Modification of the HOPG surface with GM, usually carried out by drop casting, gives rise to a homogeneous, self-ordered layer of these molecules with a thickness of less than 1 nm [ 80 , 81 ]. As is the case with pentylamine modification, GM amino groups make it possible to adsorb individual DNA molecules onto the surface and further study them by AFM [ 82 ].…”