Protein products are the basis of life on Earth and serve nearly all the functions in the essential biochemistry of life science. Each nascent protein exists as an unfolded polypeptide or random coil when translated from a sequence of mRNA to a linear chain of residues by a ribosome. The intrinsic biological functions of a protein are expressed and determined by its native three-dimensional (3D) structure that derives from the physical process of protein folding 1 , by which a polypeptide folds into its native characteristic and functional three-dimensional structure, in an expeditious and reproducible manner. Protein folding can thereby be considered the most important mechanism, principle, and motivation of biological existence, functionalization, diversity, and evolution [2] [3] [4] .
Based on the complexity of protein folding, the protein-folding problem has been summarized in three unanswered questions 1 : (i) What is the physical folding code in the amino acid sequence that dictates the particular native 3D structure? (ii) What is the folding mechanism that enables proteins to fold so quickly? (iii) Is it possible to devise a computer algorithm to effectively predict a protein's native structure from its amino acid sequence? Moreover, another essential question is why protein folding highly depends on the solvent (water or lipid bilayer) 5 and the temperature 6 ? The protein folding problem was brought to light over 60 years ago. In particular, since Anfinsen shared a 1972 Nobel Prize in Chemistry for his work revealing the connection between the amino acid sequence and the native conformation 7 , understanding of protein sequence-structure relationships has become the most fundamental task in molecular and structural biology 8 .
Protein folding is one of the miracles of nature that human technology finds quite difficult to follow, due to the very large number of degrees of rotational freedom in an unfolded polypeptide chain. In the 1960s, Cyrus Levinthal pointed out that the apparent contradiction between the astronomical number of possible conformations for a protein chain and the fact that proteins can fold quickly into their native structures should be regarded as a paradox (Levinthal's paradox) 9 , so there must be mechanisms that allow polypeptide chains to find the native states encoded in their sequence. As stated in Anfinsen's Dogma, the well-defined native 3D structures of small globular proteins are uniquely encoded in their primary structures (the amino acid sequences), is kinetically reproducible and stable under a range of physiological conditions, and can therefore be considered as an issue of the certainty.
Many proteins or protein domains, relatively rapid and efficient refolding can be observed in vitro, thus proteins may be regarded as "folding themselves" following explicit folding pathways 1 . Protein folding is considered a free energy minimization or a relaxation process that is guided mainly by the following physical forces: (i) formation of intramolecular hydrogen bonds, (ii) van der Waals interactions, (iii) electrostatic interactions, (iv) hydrophobic interactions, (v) chain entropy of protein, (vi) thermal motions 1, 10 . Among them, hydrophobic effect is normally thought to play a decisive role 11 . Currently, the generally accepted hypothesis in the field is to conceive of protein folding in a funnel-shaped energy landscape, where every possible conformation is represented by a free energy value. The rapid folding of proteins has been attributed to random thermal motions that cause conformational changes leading energetically downhill toward the native structure corresponds to its free energy minimum under the solution conditions 1, 10 . However, there are both enthalpic and entropic contributions to free energy of protein that change with temperature and so give rise to heat denaturation and, in some cases, cold denaturation 12 . So far the hypothesis haven't been able to decipher the folding code and therefore aren't generally able to read a sequence and predict what shape it will adopt.
The interaction of protein surface with the surrounding water is often referred to as protein hydration layer (also sometimes called hydration shell) and is fundamental to structural stability of protein, because non-aqueous solvents in general denature proteins 13 . The hydration layer around a protein has been found to have dynamics distinct from the bulk water to a distance of 1 nm and water molecules slow down greatly when they encounter a protein 14 . Thus, hydrophilic side chains of proteins are normally hydrogen bonded with surrounding water molecules in aqueous environments, thereby preventing the surface hydrophilic side-chains of proteins from randomly hydrogen bonding together 14,15 16 . This is the reason why proteins usually do not aggregate or crystallize in unsaturated aqueous solutions 17 , even though the solvent-facing surface of the proteins is usually composed of predominantly hydrophilic regions. Experiments have also shown that secondary structures of protein (such as -helices and -sheets) are stabilized by hydrogen bonds between the N-H groups and C=O groups of the main chain 18, 19 . This also indicates that the shielding effect of surrounding water molecules prevent hydrophilic side-chains from interfering with the formation of secondary structures during protein folding. Thus, water molecules should be able to saturate the hydrogen bond formations of hydrophilic side-chains and the main chain before the protein folding 14-16 , due to water molecules have very strong polarity 20,21 . This is the reason why intrinsically disordered proteins (IDPs) and regions (IDRs) can make up a significant part of the proteome 22 . Before the folding of secondary structures, the early steps of protein folding may be not directly dominated by the formation of intramolecular hydrogen bonds, due to the shielding effect of surrounding water molecules. Thus, this problem may lie in our lack of understanding of the hydrophobic interaction among neighbored side-chains of unfolded proteins at early steps of the folding, given the lack of awareness of the importance of the shielding effect of water.
Almost all experimentally determined native tertiary structures of water-soluble proteins have a hydrophobic core in which hydrophobic side-chains are buried from water 23-25 . Incidentally, polar residues interact favorably with water, thus the solvent-facing surface of the peptide is usually composed of predominantly hydrophilic regions 26 . Minimizing the number of hydrophobic side-chains exposed to water, namely, hydrophobic collapse thus has been regarded as one of the most important driving force for protein folding processs 27 . Experimental methods such as laser temperature jumping technology and single molecule experimental techniques have revealed that protein folding first leads to the formation of secondary structures (α-helices and β-strands), and the tertiary structure is formed by the folding of secondary structures 28 . It is likely that the nascent polypeptide forms initial secondary structure through creating localized regions of predominantly hydrophobic residues due to hydrophobic effect 29 . The secondary structures interacts with water, thus placing thermodynamic pressures on these regions which then aggregate or "collapse" into a tertiary conformation with a hydrophobic core 26 . Therefore, protein folding is highly dependent on folding of secondary structures as the way to hierarchically pave a native folding pathway that lead to formation of correct tertiary structures and cause conformational changes leading energetically downhill toward the native globular structure that possesses the minimum free energy. Thus, decipher of the folding codes in amino acid sequence that dictate the secondary structures formation should be regarded as a key to crack the protein folding problem. Among types of secondary structure in proteins, the β-sheet is the most prevalent. If the controlling mechanism for β-sheet folding can be revealed, it would remarkably promote solution of the protein folding problem.
Currently, several hypotheses has been proposed for explaining the folding mechanism of β-sheet. The hydrophobic zipper hypothesis indicates that a hairpin is first formed before hydrophobic contacts act as constraints which bring other contacts into spatial proximity 30 . This leads to further constrain and causes the rest of the contacts to zip up. Munoz et al proposed that the folding of a β-hairpin initiates at the turn and propagates towards the tails 31 . In particular, they found that stabilization through hydrophobic contacts between residues and hydrogen bonding interaction are important for the formation of the βhairpin. Petrovich et al. 32 studied a 37-residue triple-stranded β-sheet protein via MD simulations. Their results indicate that a β-hairpin first appears before the third strand joins in to complete the β-sheet at the end of the folding process. They ascribe the folding mechanism of the β-sheet to a combination of initial hydrophobic collapse and zipper mechanism, which serve to nucleate the hairpin formation. Notably, all the three mechanisms above suggest that the folding of a β-sheet is necessarily preceded by the occurrence of a β-turn. We are still missing a "folding mechanism" for β-sheets. By mechanism, we mean a narrative that explains how the time evolution of a β-sheet folding development derives from its amino acid sequence and solution conditions.
β-sheet folding highly depends on the temperature 5 , where β-sheets can form in as little as 1 microsecond after the temperature jumping 33-35 . β-sheets consist of β-strands connected laterally by at least three backbone hydrogen bonds, forming a generally pleated sheet. A β-strand is a stretch of polypeptide chain typically 3 or more amino acids long with backbone in an extended conformation. It most like that the β-strands exist before the folding of β-sheets. Because it is difficult to explain how the folding process of a β-sheet (i.e., laterally hydrogen bonding process of segments of unfolded polypeptide) is accompanied by stretching process of the segments of polypeptide into β-strands. There must be mechanisms that allow polypeptide chain segments to find the states of β-strands encoded in their sequence. There also must be some physical effects providing the long-range attractive force among βstrands for the β-sheets formation.
Experimental evidences of the folding of unfolded proteins provide corroboration for a hypothesis that folding initiation sites arise from hydrophobic interactions 11,36 . The folding of β-strands and β-sheets may be driven by hydrophobic interactions, as the nascent polypeptide may form initial primary structure through creating localized regions of predominantly hydrophobic residues 29 . Hydrophobic effect most likely can contribute to the formation of β-sheets through multistage aggregations of neighbored hydrophobic groups of unfolded polypeptides, which lead to the formation of β-strands, and consequently fold into β-sheets. A β-sheet always is amphipathic in nature, namely, contain hydrophilic surface areas and hydrophobic surface areas. Note that the hydrophobic attraction (due to the hydrophobic effect) among adjacent side-chains on one side or the other side of a β-strand may be common in experimentally determined protein structures, which should be considered as an evidence for hydrophobic effect dominating the formation of β-strands.
It has previously been noted that many amino acid side chains contain considerable nonpolar sections, even if they also contain polar or charged groups 36 . Namely, hydrophilic side-chains are not completely hydrophilic. The hydrophilicity of hydrophilic side-chains is normally expressed by C=O or N-H2 groups at their ends, and the other portions of hydrophilic side-chains are hydrophobic, because the molecular structures of these portions are basically alkyl and benzene ring structures, as shown in Figure 1 . Folding initiation sites of β-brands might therefore contain not only accepted "hydrophobic" amino acids, but also larger hydrophilic side-chains 36 . If formation of β-brands is driven by hydrophobic interactions among neighbored side-chains of unfolded polypeptide, we should be able to find experimental evidence of the hydrophobic interaction in the Protein Data Bank (PDB) achieves, due to hundreds of thousands of β-sheet structures have been experimentally determined. In an aqueous environment, the water molecules tend to segregate around the "hydrophobic" side chains of the nascent protein, creating hydration shells of ordered water molecules 37 . An ordering of water molecules around a hydrophobic region increases order in a system and therefore contributes a negative change in entropy (less entropy in the system) 38 . The water molecules are fixed in these water cages which drives the hydrophobic collapse, or the aggregation of the hydrophobic groups. Thus, the hydrophobic interaction among neighbored side-chains in sequence can introduce entropy back to the system via the breaking of their water cages which frees the ordered water molecules 39 . If hydrophobic interactions among neighbor sidechains in amino acid sequences provide the structural stability for β-brands formation, we must can find out that the phenomenon of a large hydrophobic surface area covering on one side or the other side of a β-strand is prevail in almost all experimentally determined β-sheets. If the phenomenon of hydrophobic side-chains tend to cluster together on one side of adjacent β-strands of a β-sheet is prevail in almost all experimentally determined β-sheets, we may demonstrate that the hydrophobic interaction among the neighbored side-chains responsible for β-sheet-folding initiation.
The capability of an amino acid residue to get involved in the hydrophobic attraction with neighbored residues in sequence can be evaluated by the exposed alkyl and benzene ring structures of the side-chain, as shown in Fig.1 , in which 20 kinds of amino acid residue are divided into four groups 40 . Arginine-R, Histidine-H, and Lysine-K can involve in hydrophobic interaction with adjacent hydrophobic side-chains in sequence due to their long hydrophilic side chains contain long nonpolar alkyl structures, see Fig. 2C and 2D. Noting that every β-strand is characterized by a large hydrophobic surface fully covering one side of the β-brand (the inner side), and caused each side-chains is parallel to every other side-chain of each strands due to the hydrophobic interaction. Parallel distribution of adjacent peptide planes of these β-strands also causes adjacent sidechains to distribute on opposite sides of the main chain and each carbonyl oxygen atom in a peptide plane tends to hydrogen bond with an amide hydrogen atom in an adjacent peptide plane due to the electrostatic attractions between them, except the Proline-P 15 . Parallel distribution of neighbored "hydrophobic" sidechains in a β-strand can effectively introduce entropy back to the system via the merging of the water cages of the side-chains which frees the ordered water molecules, see Fig.2D . Thus, β-strand should be considered as a metastable state for unfolded polypeptides corresponds to its free energy minimum under the solution conditions, creating localized regions of predominantly hydrophobic side-chains 15 .
We use another small-molecule protein (PBDID:1OUR) as the example to demonstrate the role of hydrophobic interactions among neighbored side-chains played in formation of β-strands, β-turns and βsheets, see Fig.3 . The protein is mainly composed with β-strands and 10 β-turns. Every β-strand of the protein is also characterized by a large hydrophobic surface fully covering one side or the other side of the β-brand, see Fig.3A . Aspartate-D, Asparagine-N, Serine-S, Proline-P, Glycine-G most likely contribute to formation of β-turns in protein folding, due to the other neighbored side-chains in amino acid sequence tend to hydrophobic attract with each other through bypassing these residues (see Fig.1d ).
Thereby, Aspartate-D, Asparagine-N, Serine-S, Proline-P, Glycine-G can be classified as a hydrophobic blocking (RB) group. It is worth noting that almost all the 10 β-turns of the protein are composed with two or more residues of Aspartate-D, Asparagine-N, Serine-S, Proline-P, Glycine-G, see Fig.3A and 3B. This indicates that two or more adjacent RB residues can effectively block hydrophobic attraction among neighbored side-chains in sequence at both side of a strand. We plot the protein structure into three parts according to three segments of the amino acid sequence to illustrate the hydrophobic collapse among neighbored β-strands in sequence, see Fig.3B and 3C. Hydrophobic interactions among these β-strands may drive them collapse together through bending the unfolded polypeptide at the location of these RB residues, namely, bypassing these RB residues at the turns to achieve the hydrophobic collapse. This also indicates that hydrophobic attraction among neighbored side-chains drive the β-strands formation and then cause hydrophobic attraction among the neighbored β-strands and formation of the β-sheets, due to β-strands formation create localized regions of predominantly hydrophobic residues and place thermodynamic pressures on these regions under the solution conditions. Formation of β-sheets also make β-strands aggregate or "collapse" into a tertiary conformation with a hydrophobic core.
Thereby, we speculate that folding of β-sheets is triggered by multistage hydrophobic interactions among neighbored side-chains of unfolded polypeptides, enable β-sheets fold reproducibly following explicit physical folding codes in aqueous environments.
We use 1000 experimentally determined small protein structures to further demonstrate the hydrophobiceffect-based folding mechanism for β-sheets. All the 1000 small proteins were randomly selected from the PDB. 3235 β-strands can be identified in the 1000 protein structures by using the PDB archive and the STRIDE software 42 . From analysis of all the 3235 β-strands of the 1000 proteins in PDB, we find out that the feature of hydrophobic attraction (due to the hydrophobic effect) among adjacent side-chains on one side or the other side of a β-strand covering the length of the β-strand is prevail in all the experimentally determined β-strands (see Supplementary S5 ). This indicates that the hydrophobic interaction among the neighbored side-chains responsible for the formation of β-strands.
Aspartate-D, Asparagine-N, Serine-S, Proline-P, Glycine-G can't effectively hydrophobic attract with neighbored side-chains in sequence, see Fig.1D . Thus, Aspartate-D, Asparagine-N, Serine-S, Proline-P, Glycine-G most likely lead to β-turns formation in protein folding, due to the other neighbored sidechains in amino acid sequence tend to hydrophobic attract with each other through bypassing these residues. The β-turn is the third most important secondary structure after helices and β-strands. β-turns have been classified according to the values of the dihedral angles φ and ψ of the central residue. β-turns can be easily identified in between β-strands or α-helices of the protein structures using the PDB archive and the STRIDE software 42 . We identified 5776 β-turns in the 1000 protein structures, include about 1780 β-hairpin turns. We find out that about 97.4% of the β-turns contain at least one Aspartate-D, Asparagine-N, Serine-S, Proline-P or Glycine-G residue 43 , as illustrated in Supplementary 2.
Whereas, most of the rest no-RB β-turns contain at least one Glutamate-E, Glutamine-Q, Threonine-T, and Alanine-A residue. This indicates that Glutamate-E, Glutamine-Q, Threonine-T, and Alanine-A may contribute to the formation of β-turns due to their exposed hydrophobic proportions is relatively small.
Moreover, about 99.3% β-hairpin turns contain at least one Aspartate-D, Asparagine-N, Serine-S, Proline-P or Glycine-G residue, see Supplementary 2. Two RB residues coded together normally shouldn't be able to present at the middle of a long straight βstrand. Because the other residues of the strand at both sides of the two RB residues tend to hydrophobic aggregate together and thus would bend the strand at the two RB residues to achieve the hydrophobic interaction. However, we can still identified 29 long β-strands (each β-strands contain more than 12 residues), which are characterized by two adjacent RB residues locating at the middle of the β-strands through scanning the 1000 protein structures by using the STRIDE software 42 . By checking these long β-strands using PyMOL software, we find out that 24 of these long β-strands actually curved exactly at their two RB residues in the amino acid sequences, demonstrating the capability of RB residues to cause β-turns formation, see Fig. 4 . The other 5 long β-strands either have three or more RB residues coded together or have RB residues located at one end of the strands that make the hydrophobic blocking region extend to the ends of these β-strands, thus undermining the hydrophobic interaction between the both ends of these β-strands, see Supplementary S3. The long β-strand of the 1YV7 protein curved at a sequence segment of threonine-threonine-terine-glutamate (TTSE), see Supplementary S3. This indicates that Glutamate-E, Glutamine-Q, Threonine-T, and Alanine-A may also contribute to the formation of β-turns due to their exposed hydrophobic proportions is relatively small.
The spike (S) protein of novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)
is of great concern due to the coronavirus disease 2019 (COVID-19) pandemic. The D614G mutation in SARS-CoV-2 begin to receive widespread attention for its rising dominance worldwide. This mutation changes the amino acid at position 614, from D (aspartic acid) to G (glycine), the initial D614 is now the G614 variant. It is worth noting that the amino acid at position 614 is located at a β-turn in a tertiary structure of the spike. This is consistent with our new theory that both D (aspartic acid) to G (glycine) can result in the β-turn formation. The D-614-G nutation may accelerate the folding of the quaternary structure of the spike due to G614 most likely can contribute to the hydrophobic effect between two tertiary structures of the protein rather than the D614 (see Fig.1D ), due to the position 614 located at the docking site in between them.
A typical β-hairpin structure contains two β-strands with hydrophobic attraction between each side-chain and every other side-chain on the strands. Thus, we might be able to predict β-hairpin structures through evaluating hydrophobic attraction among each side-chain with every other side-chain in the primary structure of a protein. We may can predict β-hairpin through identifying two neighbored sequences of residues in the polypeptide chain both characterized by hydrophobic attraction between each side-chain to every other side-chain, and have two RB in between them. By using this method, we identified 553 samples in terms of the characteristics above from the 1000 proteins. We find that 158 of the samples are β-hairpins, 36 of the samples are structures of strand-turn-strand, 296 of the samples are structures of strand-turn-helix, 23 of the samples are structures of coil-turn-strand, 23 of the samples are coil-turncoil and 6 of the samples are α-helices. Thus, physical folding codes for β-hairpins and strand-turn-strand can be deciphered through evaluating hydrophobic interaction among side-chains of an unfolded polypeptide. The results show that strand-turn-helix also can be predict by the method. This indicates that folding of α-helix may be initiated from a β-strand-like thermodynamic metastable state 15 .
Many amino acid residues contain considerable nonpolar sections in their side-chains, even if they also contain polar or charged groups. This make hydrophobic interaction among neighbored amino acid sidechains in amino acid sequence of polypeptides becomes an important driving force for the stabilization of initial thermodynamic state of unfolded Proteins. The feature of a large hydrophobic surface area covering most side-chains on one side or the other side of adjacent β-strands of a β-sheet is prevail in almost all experimentally determined β-sheets. Minimizing the exposed hydrophobic portions of adjacent side-chains to water should be regarded as the most important driving force for the β-strands formation and caused each side-chains is parallel to every other side-chain on strands. β-turns often contain residues of Aspartate-D, Asparagine-N, Serine-S, Proline-P, Glycine-G which characterized with their sidechains having very small hydrophobic proportions exposure, that is explained as these residues can block hydrophobic effect among neighbored side-chains in sequence, thereby contribute to turns formation.
The folding of β-sheets are most likely triggered by multistage hydrophobic interactions among neighbored side-chains of unfolded polypeptides, enable β-sheets fold reproducibly following explicit physical folding codes in aqueous environments. Temperature dependence of the folding of β-sheet is thus attributed to temperature dependence of the strength of the hydrophobicity. The hydrophobic collapse of β-strands into β-sheets most likely trigger enthalpy-entropy compensation of unfolded polypeptides, enable the main-chain of β-strands to get rid of the hydrogen-bonded water molecules and laterally hydrogen bonding with each other. The folding codes in amino acid sequence that dictate the formation of a β-hairpin can thus be deciphered through evaluating hydrophobic interaction among sidechains of an unfolded polypeptide from a β-strand-like thermodynamic metastable state.
In this study, many experimentally determined native structures of proteins are used to study the folding mechanism of β-sheets. All the three-dimensional (3D) structure data of protein molecules are resourced from the PDB database. IDs of these proteins according to PDB database are marked in the Fig.2, Fig.3 , and Fig.4 . In order to show the distribution of hydrophobic areas on the surface of β-strands and β-sheets in these figures, we used the structural biology visualization software PyMOL to display the hydrophobic surface areas of these secondary structures.
Secondary structures of β-strands, β-turns, β-sheets and α-helices were identified in the 1000 proteins by using the STRIDE software 42 . We also used molecular 3D structure display software PyMOL to confirm the identification of secondary structures of proteins. Long β-strands (more than 12 residues) characterized with two adjacent RB residues located at the middle of the β-strands and curved exactly at their two RB residues in the amino acid sequences. 134L  1KP4  1Z3L  3C3G  4IC9  1FDD  1R75  2OAI  3OZZ  5HBP  155C  1KSM  1Z3M  3C4S  4IDL  1FE3  1R9H  2OJR  3P2X  5HBQ  1A0B  1KTH  1Z3P  3C5K  4IP1  1FE5  1RAQ  2OLI  3PAZ  5HDG  1A18  1KXI  1ZIA  3C7I  4IP6  1FER  1RBI  2ON8  3Q1D  5HJC  1A6F  1KXW  1ZIB  3C97  4IPF  1FES  1RBW  2OPY  3Q4Y  5HKN  1AA2  1KXX  1ZJ7  3CE8  4JHB  1FEV  1RBX  2OQK  3Q7Y  5HMB  1AB0 1KXY 5LAW  1B0T  1LXI  2B4A  3ETW  4LYO  1FOW  1RRI  2P8V  3SGP  5LAZ  1B1E  1LYO  2B8G  3EZM  4MDQ  1FOY  1RRY  2PAL  3STM  5LN2  1B1I  1LZ4  2B9D  3F3Q  4MJJ  1G2S  1RS2  2PK7  3SUL  5M9A  1B1J  1M1S  2BEZ  3F45  4ML2  1GBQ  1RSI  2PKT  3T1X  5MXY  1B1U  1M4A  2BFH  3F8C  4MZ2  1GD6  1RTU  2PNE  3T3J  5NGN  1B2O  1M4B  2BHK  3FAJ  4N0Z  1GDC  1RWJ  2PPI  3T8R  5NWX  1B6E  1M4M  2BHO  3FFY  4N5T  1GHJ  1RZY  2PPN  3T8T  5O3A  1BAS  1MB3  2BO1  3FRV  4N6J  1GKH  1S3P  2PVT  3UAF  5OC4  1BEA  1MG6  2BPP  3FWU  4NEJ  1GMG  1S7I  2PW5  3UB2  5OC8  1BEL  1MH7  2BQQ  3FYR  4NXR  1GOD  1SDZ  2PWS  3UB3  5OMD  1BFE  1MH8  2BRF  3FZ9  4OOH  1GP3  1SF6  2PYK  3UB4  5PAL  1BGI  1MK0  2BS5  3FZA  4OV1  1GS3  1SF7  2PZW  3UMD  5PAZ  1BHF  1MKU  2BTI  3G7C  4OXW  1GSW  1SFB  2Q1M  3UME  5RHN  1BKF  1ML8  2BWK  3GBQ  4OZL  1GV2  1SFG  2QAS  3UNN  5RNT  1BKV  1MLI  2BWL  3GK2  4P15  1GVP  1SKZ  2QDB  3V19  5TAB  1BM2  1N9N  2BZY  3GK4  4P2P  1GXT  1SNP  2QHE  3V1G  5U9U  1BMG  1N9O  2CDS  3GKY  4P7U  1H2P  1SNQ  2QHW  3VXW  5UEP  1BO0  1NEH  2COQ  3GLW  4P9E  1HD0  1SSC  2QIU  3VYA  5UER  1BPQ  1NEQ  2CW4  3GM2  4P9V  1HE7  1SV9  2QNW  3WIT  5UES  1BQK  1NKO  2CXY  3GM3  4PAZ  1HEH  1T00  2QR3  3WRP  5UET   1BQR   1NLO  2D4L  3GQU  4PE7  1HEY  1T1D  2QVT  3WUN  5UEV  1BU3  1NN7  2D4M  3GSP  4PTA  1HFX  1T2J  2R2Y  3WVT  5UEY  1BXY  1NNX  2D58  3H33  4QYW  1HIK  1TAY  2R34  3WW5  5USV  1BYL  1NXT  2DB7  3H9W  4RLM  1HKF  1TCY  2R36  3WX4  5UVS  1C0B  1NXV  2DH1  3HAF  4RLN  1HME  1TDY  2R39  3ZEK  5UVY  1C0C  1O2E  2DP9  3HAK  4RUD  1HQ8  1TEN  2REA  3ZK0  5UVZ  1C76  1O3X  2DRT  3HEY  4TQN  1HQB  1TGJ  2REY  4AHG  5VEA  1C9H  1O41  2DU9  3HFF  4TS8  1HRC  1TNS  2RKN  4AHI  5VR3  1C9V  1O42  2DYQ  3HFN  4UNG  1HRQ  1TS9  2RLN  4AHN  5WOR  1CDP 1O43 6CE8  1DDV  1O4M  2FKL  3IRC  4ZC3  1IOR  1UID  2WOR  4DP2  6CEA  1DDW  1O4N  2FLS  3J4G  5AEF  1IOS  1UIE  2WOS  4DP4  6CEC  1DKJ  1O4O  2FLT  3JTE  5AFG  1IOT  1UIF  2WQ0  4E1P  6CED  1DMM  1O4Q  2FMB  3JZR  5AI2  1IR7  1UIG  2WQ3  4E1R  6CEE  1DMN  1O4R  2FO3  3K0X  5B1F  1IR8  1UKU  2WQH  4EC2  6CEF  1DMQ  1O5J  2FQL  3K63  5B1G  1IR9  1UPJ  2X44  4EES  6DXH  1DPY  1O7Z  2FTB  3K6D  5B3Q  1IRQ  1UPR  2X9C  4ET8  6DXR  1DQ7  1OAP  2GSP  3K9I  5B52  1IRW  1UVY  2XBD  4ET9  6EKB  1DYZ  1OB6  2GV2  3KD0  5B79  1ISU  1UW3  2XCZ  4ETA  6EVL  1DZ0  1OD7  2H2B  3KHQ  5BMH  1IYU  1UW7  2XDY  4ETB  6EVM  1E5B  1ODA  2H36  3KLU  5BPO  1IZA  1UWM  2XFE  4ETD  6FCE  1E6K  1OOI  2H46  3KMJ  5C39  1J2V  1V07  2XKH  4ETE  6FGL  1E6L  1OPY  2H8A  3KQ6  5C4P  1J4H  1V46  2XMU  4EWW  6FGT  1E6M  1OR5  2H8V  3KQI  5C68  1J4I  1VAT  2YHN  4EWZ  6FGU  1E97  1P0R  2H95  3KTP  5C6X  1J73  1VED  2YWZ  4EX0  6FH6  1EA2  1P65  2HB4  3KU7  5CB9  1J7Z  1VER  2YXY  4F1A  6FH7  1ECW  1P9G  2HC8  3KVT  5CO9  1J81  1VHF  2Z44  4F2E  6FXF  1ED1  1PAL  2HPL  3L1M  5CPV  1J82  1VIH  2Z7J  4F68  6GF0  1EFQ  1PAZ  2HWV  3L6W  5CUL  1JC7  1VMG  2ZGD  4F69  6H0K  1EIF  1PBI  2I9V  3LHC  5D53  1JDL  1W2L  2ZHH  4F6D  6H0L  1EIG  1PI8  2IGP  3LJM  5D54  1JER  1W6X  3A0D  4FC1  6HA4   1EMN   1PKS  2IIY  3LLH  5DKN  1JHC  1WAQ  3A0S  4FDX  6I3S  1EN2  1PO8  2INT  3LMF  5DM9  1JKD  1WHI  3A0V  4FE6  6I5A  1ENV  1PZ4  2J5A  3LR0  5DZD  1JOI  1WJG  3A7L  4G3O  6IFH  1EOQ  1PZA  2JIN  3LVE  5E0Z  1JON  1WJX  3ADY  4G4W  6INS  1EOT  1PZB  2JK7  3LYO  5E4P  1JPE  1WRP  3AZ5  4G4X  6IQC  1EOW  1PZC  2JP8  3LZ2  5E4X  1JPO  1WY9  3B7X  4GBC  6JQ4  1EQV  1Q4R  2JVH  3M4T  5EE2  1JZA  1XW3  3B84  4GBN  6MHN  1EV3  1Q4V  2KRI  3MAZ  5EH4  1K1Z  1XW4  3BF2  4GFY  6MPM  1F1W 1Q7O 