You will be presented with the abstract, introduction, and discussion section from a biomedical research article. Your task is to create a summary that a layperson can understand, capturing the essence of the research article. Keep essential scientific terms, but ensure that the language remains clear and the concepts are explained in an uncomplicated manner.

Title: Hydrophobin Film Structure for HFBI and HFBII and Mechanism for Accelerated Film Formation}
Article:
Abstract:
Hydrophobins represent an important group of proteins from both a biological and nanotechnological standpoint. They are the means through which filamentous fungi affect their environment to promote growth, and their properties at interfaces have resulted in numerous applications. In our study we have combined protein docking, molecular dynamics simulation, and electron cryo-microscopy to gain atomistic level insight into the surface structure of films composed of two class II hydrophobins: HFBI and HFBII produced by Trichoderma reesei. Together our results suggest a unit cell composed of six proteins; however, our computational results suggest P6 symmetry, while our experimental results show P3 symmetry with a unit cell size of 56 Å. Our computational results indicate the possibility of an alternate ordering with a three protein unit cell with P3 symmetry and a smaller unit cell size, and we have used a Monte Carlo simulation of a spin model representing the hydrophobin film to show how this alternate metastable structure may play a role in increasing the rate of surface coverage by hydrophobin films, possibly indicating a mechanism of more general significance to both biology and nanotechnology.
Introduction:
Hydrophobins are a group of proteins produced by filamentous fungi[1]–[4]. They assemble at surfaces, and perform their function through the alteration of these surfaces. Functions performed by hydrophobins through this mechanism include the lowering of the surface tension of water, and adding a hydrophobic coating to the mycelia to allow for aerial growth[5], adhesion to surfaces[6], and coating of a variety of fungal structures[7],[8]. Hydrophobins can be seen as a mechanism through which the fungi fine tune the properties of interfaces in their environment, resulting in their invasive and adaptive behaviour. When hydrophobins locate to surfaces they are known to form assemblies with long range order[9]–[11]. In addition, the presence of hydrophobin coatings on interfaces is known to affect the properties of the interfaces in a highly specific fashion, beyond merely decreasing surface tension. In particular it has been observed that hydrophobin films at the air-water interface have an elasticity orders of magnitude higher than that observed for other surfactants[12]. Surface-adhered hydrophobin films also display additional unique characteristics[13]. Hydrophobins are divided into two classes, class I and class II hydrophobins. For class I, highly characteristic structures, named rodlets[14], are formed. An example of a class I hydrophobin is the hydrophobin EAS[15],[16]. Class II hydrophobins do not show rodlet structures, instead, they are amphiphilic and form 2D crystalline films on the air-water interface, as confirmed through grazing incidence small angle X-ray scattering( GISAXS)[9]–[11]. In both cases, the unique macroscopic properties observed in hydrophobin films will arise from cooperative effects in the stabilisation of the film that result from the interactions between the interlocking proteins in the structured surface network that they form. In addition to their role as an adaptive strategy of the fungi that produce them, the interfacial assemblies of hydrophobins have led to numerous industrial applications[17]. Examples include foams[18], protein immobilisation[19], emulsification[20], and dispersion of insoluble compounds[21],[22]. Most of these applications rely on the unique properties of the interfacial films that hydrophobins form. It is particularly noteworthy that the above mentioned exceptional properties can be found on a wide variety of different interfaces, including liquid-liquid and gas-liquid interfaces. Two hydrophobin proteins, that are of particular interest in relation to their possible industrial applications, are produced by Trichoderma reesei, known as HFBI and HFBII, that belong to the class II family of hydrophobins. Their property of forming amphiphilic 2D crystalline structures at the air-water interface, rather than rodlet structures, allows for these structures to be transferred to hydrophobic surfaces where they play a role in bringing macromolecules, to which the proteins are attached, to these surfaces, for example hydrophobic nanoparticles[22]. Some progress has been made in the determination of the structure and mechanisms involved in the formation of HFBI and HFBII films. The first high resolution structure of a hydrophobin, determined through x-ray crystallography, was obtained for HFBII of T. reesei[23]. It was found that the protein structure is crosslinked by disulphide bridges and has a diameter of approximately 2 nm. A clearly distinguishable patch on one side of the protein consists of only aliphatic amino acid side chains. This results in an amphiphilic structure with an exposed and flat hydrophobic face. A high resolution crystal structure has now also been determined for HFBI[24], showing a similar structure. Further insight into the structure of films of HFBI and HFBII has been obtained from GISAXS[9]–[11] and Langmuir-Blodget films[9], indicating a triangular lattice symmetry[9] with unit cell sizes of 55 and 56 Å respectively. We have combined cryo-EM measurement, protein-protein docking and molecular dynamics simulation, to obtain a detailed atomic resolution picture of the assembled structure of hydrophobin films at the air-water interface. We have studied the structures of HFBI and HFBII of T. reesei for which high resolution structures of both are available[23]–[27]. Our protein-protein docking results indicate a unit cell composed of six proteins with a structure very close to a P6 2D point group symmetry class[28]. Electron cryomicroscopy results, however, indicate a structure with only P3 symmetry- possibly a structure connecting two air-water interfaces in a thin film. In addition, through the protein-protein docking results we have found a possible metastable structure with P3 symmetry and a smaller lattice size, and have used a Monte Carlo simulation of a simplified model of the surface to demonstrate the role this alternate possible ordering could have in the formation of the surface structure.
Discussion:
Along with this text there are a set of atomic model files included in PDB format. The. zip file “Dataset_S1” contains eight. pdb files. For each of the three hexamer structures( α( A) and β( B) for HFBI and HFBII) there is one copy of the raw docking result with suffix “_raw” and one copy of the six protein structure squeezed to the experimental lattice parameters under pressure of 54 and 55 Å respectively( Kisko et al.[11]) with suffix “_exfit”. For all cases the lattice vectors are along the x axis and rotated 120° counterclockwise from the x axis. Thus for HFBI with the lattice distance constrained to match the experimental system the lattice vectors are a = 54. 00, 0. 0, 0. 0 b = −27, 46. 765, 0. 0 and for HFBI α structure with raw docking fit a = 54. 723, 0. 0, 0. 0 b = −27. 362, 47. 392, 0. 0, HFBI β is a = 57. 113, 0. 0, 0. 0 b = −28. 557, 49. 461, 0. 0. For HFBII the lattice vectors are a = 64. 537, 0. 0, 0. 0 b = −32. 269, 55. 891, 0. 0 and when constrained to fit the experimental lattice size a = 55. 0, 0. 0, 0. 0 b = −27. 5, 47. 631, 0. 0. The two structures of the metastable low density P3 structure with the three protein unit cell are also included. Both of these structures are aligned in the xy plane with lattice axis along x axis, like the six protein structures, and include a triangle of three unit cells. The Supplementary tables “Table_S1. pdf”, “Table_S2. pdf” and “Table_S3. pdf”, are also included, with S1 and S2 concerning details of the electron cryo-microscopy results, and S3 concerning results from the molecular dynamics simulation. The animation “Movie_S1. mpg” demonstrates the simple transition between the P6 and extended P3 2D crystal structures, described in the text.
Filamentous fungi release a specific type of protein , belonging to a protein family known as “hydrophobins” into their environment to control interfaces in a fashion that promotes growth . Such protein coatings are the mechanism that allows for the mycelia to grow out of the water and into the air . When these hydrophobins form films at the air-water interface and on the surface of solid objects immersed in water , they impart properties to those surfaces that has led to their use in a wide range of industrial applications . Of particular interest is the properties they impart to air liquid interfaces , and as a mechanism to bring protective materials to coat nanoparticles in nanotechnology applications . A more detailed knowledge of the structure of these surfaces will allow for augmentation of their function that is possible through genetic engineering of the hydrophobins themselves . In this study we have combined computational and experimental methods to develop atomistic level insight into the structure of this surface for two important hydrophobins: HFBI and HFBII of Trichoderma reesei . In addition to insight into the surface structure , we have uncovered an intriguing possible new mechanism for film formation , which may explain some of the striking properties of hydrophobin films , and could be extended to a more general mechanism .