The recently identified Mulberry Mosaic Dwarf-associated Virus (MMDaV), associated with mosaic dwarf symptoms in Chinese mulberry leaves, is a newly discovered member of the Geminiviridae family. The MMDaV genome, a single or twin circular single-stranded DNA molecule measuring approximately 2.5-3.0 kb, encodes five proteins and two hypothetical proteins, including a coat protein (CP) and movement protein (MP). The co-evolutionary dynamics between viral and host codon usage significantly impact viral survival, fitness, immune evasion, and evolutionary pathways. This study applied bioinformatic analyses to examine the codon usage bias in thirty MMDaV genomes collected from mulberry leaves in four distinct Chinese provinces. We aimed to understand the drivers of preferred synonymous codon usage. The Effective Number of Codons (ENC) analysis revealed significant regional variations among MMDaV isolates, allowing their classification into two main categories: the southern China HNZX strain and the eastern China HDZX strain. The codon preference analysis displayed a viral preference for using A/U as the terminal base, indicating a bias towards A/U over G/C. Using a combination of position-specific base composition, ENC-Plot, RP2-Plot, Neutral plot, and correspondence analysis, we found that mutational pressure and natural selection substantially influence codon usage and drive MMDaV evolution. Our findings shed light on the complex interplay between MMDaV and its mulberry host and offer crucial insights into the virus's adaptive and evolutionary mechanisms.

Phylogenies depict shared evolutionary patterns and structures on a tree topology, enabling the identification of hierarchical and historical relationships. Recent analyses indicate that phylogenetic signals extend beyond the primary structure of protein or DNA, and various aspects of codon usage biases are phylogenetically conserved. Several functional biases exist within genes, including the number of codons that are used, the position of the codons, and the overall nucleotide composition of the genome. Codon usage biases can significantly affect transcription and translational efficiencies, leading to differential gene expression. Although systematic codon usage biases originate from the overall GC content of a species, ramp sequences, codon aversion, codon pairing, and tRNA competition also significantly affect gene expression and are phylogenetically conserved. We review recent advances in analyzing codon usage biases and their implications in phylogenomics. We first outline common phylogenomic techniques. Next, we identify several codon usage biases and their effects on secondary structure, gene expression, and implications in phylogenetics. Finally, we suggest how codon usage biases can be included in phylogenomics. By incorporating various codon usage biases in common phylogenomic algorithms, we propose that we can significantly improve tree inference. Since codon usage biases have significant biological implications, they should be considered in conjunction with other phylogenetic algorithms.

Codon use bias is an important characteristic in the process of genetic information transmission of species. With the publication of the genome of C. panzhihuaensis, it is of great significance to investigate the codon use bias for understanding the genetic evolution of this species and for molecular breeding. In this study, Perl language and CodonW 1.4.2 software was used to systematically analyze the coding gene sequences of the C. panzhihuaensis genome, obtain the characteristics of codon use, and identify the sources of variation affecting codon use. The results showed that GC3s content, GCall content, and ENC value were 46.75%, 47.67%, and 52.8 respectively. As the first seed plant, the GC3 content of Cycas is similar to that of most gymnosperms and most dicotyledons, but considerably different from that of monocotyledons.RSCU value was greater than 1, among which 21 codons ended in U or A. Enc-plot analysis, PR2-plot neutral plot analysis, and correlation coefficient analysis of Axis1 with GC3s and CAI revealed that the codon bias was mainly affected by natural selection, but also by mutation pressure and other factors. Thirty-one optimal codons of Cycas genes were screened. This research can provide a reference for the phylogeny and genome codon evolution of Cycas.

Chaphamaparvovirus (ChPV) is an ancient virus that has been detected in a variety of hosts. In this study, based on the phylogenetic analysis and the adaptability of ChPV to multiple hosts, we evaluated the potential of feline (FeChPV) and canine ChPV (CaChPV) for cross-species transmis-sion. Phylogenetic analysis showed that FeChPV and CaChPV were closely related. Notably, two strains of ChPVs isolated from domestic cats and 2 from dogs clustered together with CaChPVs and FeChPVs, respectively, suggesting the stringent boundaries between canine and feline ChPV may be broken. Further analysis revealed that CaChPV and FeChPV were more adapted to dogs than to cats, strongly suggesting the possibility of unidirectional or bidirectional transmission be-tween dogs and cats. Mutation analysis identified several shared mutations in cross-species-transmissible strains that were not located within immune epitopes. Furthermore, the VP struc-tures of FeChPV and CaChPV exhibited a high degree of similarity across both cross-species-transmissible and non-cross-species-transmissible strains. However, definitive experimental evi-dence is lacking, and its capacity for cross-species transmission should be approached with cau-tion and elucidated in further studies.

The Standard Genetic Code (SGC) exists in every organism known on Earth. SGC evolution via early unique codon assignment, then later wobble, yields coding resembling the near-universal code. Below, later wobble also creates an optimal route to accurate codon assignment. This assignment time matches a previous mean time for ordered codes, exhibiting ≥ 90% of SGC order. Accurate evolution is also accessible, sufficiently frequent to appear in populations of 10³ to 10⁴ codes. SGC-like coding capacity, code order and assignments therefore arise together, in one attainable evolutionary intermediate. Examples, which plausibly resemble coding at evolutionary domain separation, are characterized.

Dengue is a pan-tropical arthropod-borne disease, endemic in over 100 countries. The dengue virus comprises four antigenic serotypes (DENV 1-4). The envelope (E) and non-structural 1 (NS1) proteins are highly immunogenic, and the E protein carries epitopes eliciting neutralizing antibodies. In previous studies, mice immunizations with two DNA vaccines encoding the E ectodomain (pE1D2) and NS1 proteins (pcTPANS1) from DENV2 induced high protection. Based on these findings, we constructed new plasmids containing the codon-optimized genes from these proteins for expression in mouse and human cells, named pEotmD2 and pNS1otmD2. Compared to the pE1D2, the pEotmD2 mediated lower expression of the recombinant protein in human and mouse cell lines, while the pNS1otmD2 plasmid was slightly more efficient than the pcTPANS1 in these cells. Immunogenicity and protection were evaluated in BALB/c mice immunized with the original and codon-optimized plasmids followed by challenged with DENV2. In accordance with the in vitro experiments, the antibody response and protection elicited by the pE1otmD2 plasmid was lower than those observed with the pE1D2. In contrast, the pNS1otmD2 vaccine enabled slightly higher levels of the humoral and protective responses than the pcTPANS1. Overall, our study revealed different effects of codon optimization on these two dengue DNA vaccines.

Colorectal cancer (CRC) is the third most common cancer, with rising incidence due to lifestyle and diet. 40% of CRC cases are found to have KRAS mutations. In this study, we investigate the survival outcome of metastatic Colorectal cancer mCRC) patients in Brunei Darussalam restrospectively. Chi-squared test was used to compare the survival outcomes of mCRC patients, and Mann-Whitney U test was used to compare the median ages of both groups. Kaplan-Meier survival curves were drawn and logrank test was used to compare the survival outcome between two groups. There was a total of 105 patients with stage IV CRC being treated during the study period. 81.6% (n=62) of mCRC patients were found to have the primary tumours on the left side of the colon. 19 of these 26 (73.1%) mutant KRAS mCRC patients died, while 23 of 50 (46.0%) wild-type KRAS mCRC patients died at the end of the study period, contributing to death rates of 45.2% and 54.8%, correspondingly. 30.3% (n=23) of the study population had a single metastatic site detected (either liver, or lung or any other organs), while 69.7% (n=53) of the 76 mCRC patients had two (double) or more metastatic sites. 69.2% (n=18) and 30.8% (n=8) of the mutant KRAS mCRC patients had mutations within codons 12 and 13, respectively. To our knowledge, this is the first study in Brunei Darussalam to analyse both the survival outcomes of metastatic CRC patients and those of mutant KRAS mCRC patients. Chi-squared analysis showed a significant difference between the survival outcomes of wild-type KRAS and mutant KRAS mCRC patients (p-value = 0.024). There was a significant difference in the survival outcome between the mutant KRAS mCRC patients with RCC and mutant KRAS mCRC with LCC patients. There was no significant difference between the survival outcomes of mutant KRAS patients with mutations in either codon 12 or 13 of the KRAS gene (Table 3). However, there is a significant difference in the median survival periods between the mutant KRAS mCRC patients with mutations in codon 12 and those with mutation in codon 13 of the KRAS gene (p-value = 0.003). In conclusion, we found that mutant KRAS mCRC patients had a significantly poorer OS, which was shown to be worse when the primary tumours were found at the left side of the colon. Mutant KRAS mCRC patients with mutations in codon 12 were found to have shorter survival median periods than those with mutations within codon 13.

The HIV-1 nef gene terminates in a 3’-UGA stop codon, which is highly conserved in the main group of HIV-1 subtypes, along with a downstream potential coding region that could extend the nef protein by 33 amino acids, if readthrough of the stop codon occurs. Antisense tethering interactions (ATIs) between a viral mRNA and a host selenoprotein mRNA are a potential viral strategy for the capture of a host selenocysteine insertion sequence (SECIS) element (Taylor et al, 2016) [1]. This mRNA hijacking mechanism could enable the expression of virally encoded selenoprotein modules, via translation of in-frame UGA stop codons as selenocysteine (SeC). Here we show that readthrough of the 3’-terminal UGA codon of nef occurs during translation of HIV-1 nef expression constructs in transfected cells. This was accomplished via fluorescence microscopy image analysis and flow cytometry of HEK 293 cells, transfected with engineered GFP reporter gene plasmid constructs, in which GFP can only be expressed by translational recoding of the UGA codon. SiRNA knockdown of thioredoxin reductase 1 (TR1) mRNA resulted in a 67% decrease in GFP expression, presumably due to reduced availability of the components involved in selenocysteine incorporation for the stop codon readthrough, thus supporting the proposed ATI. Addition of 20 nM sodium selenite to the media significantly enhanced stop codon readthrough in the pNefATI1 plasmid construct, by >100%, supporting the hypothesis that selenium is involved in the UGA readthrough mechanism.

The furin cleavage site, with an arginine doublet (RR), is one of the clues of the SARS-CoV-2 origin. This furin-RR is encoded by the CGG-CGG sequence. Because arginine can be encoded by six codons, in a previous work we found that in SARS-CoV-2, CGG was the minority arginine codon (3%). Also, analyzing the RR doublet from a large sample of furin cleavage sites of several kinds of viruses, we found that none of them were encoded by CGG-CGG. Here, we come back to the core of the matter, but from the perspective that in the human genome, in contrast, CGG is the majoroty arginine codon (21%). Here, we highlighted that the 6 arginine codons provide genetic markers to a traceability on the RR origin in the furin site, as well as, to weigh the probability of the theories about the origin of the virus.

Single molecule de novo protein sequencing based on the 'superspecificity' of amino-acyl tRNA synthetases (aaRS) is proposed. An unfolded protein molecule is threaded through a nanopore in an electrolytic cell (e-cell) to expose the terminal residue in the e-cell's trans chamber. After the residue is cleaved with an exopeptidase, a set of tRNAs, their aaRSs, and ATP are added to trans. An aaRS charges a cognate tRNA molecule with the residue. The charged tRNA (along with the other reactants) is transferred to an extended e-cell with N (20 ≤ N ≤ 61) pores in N individual cis chambers and a single trans chamber. Each pore holds an RNA molecule ending in a unique codon that is exposed in trans. The charged tRNA's anticodon base-pairs with the terminal codon of an RNA. If tRNAs and residues are fluorescently tagged with two different colors, the residue can be identified from the observed position of the resulting color pair. As charging is 'superspecific' identification is unambiguous. The protein molecule in the first e-cell is advanced by one residue and the process repeated. In this approach there is no need for precise pore current or optical intensity measurements. Potential implementation issues are discussed. Other possibilities, including one in which the terminal residue is cleaved after charging, are also examined.

The intricacies of translational strategies make this stage of the implementation of genetic information one of the most difficult to understand and, at the same time, perhaps the most interesting. It also becomes clear that all this variety of strategies is not just a consequence of a long evolutionary history but is of paramount importance for fine-tuning gene expression and metabolic modulation. This is especially true for those organisms that demonstrate predominantly biochemical and physiological reactions with a lack of behavioural ones. Plants are just such a group of organisms. Overcoming unfavourable environmental conditions occupies a key place in plant physiology. This is especially true with the changing conditions of global warming and the irretrievable loss or depletion of natural ecosystems. Conceptually, the response of plants to abiotic stress is a set of complex and intricate strategies. This is dictated both by a variety of abiotic factors that provoke stressful conditions and by a variety of molecular genetic mechanisms that make it possible to fine-tune the metabolic pathways through which the plant organism overcomes non-standard and non-optimal conditions. In the presented review, we tried to focus on the state-of-the-art in the field of translational regulation in plants under abiotic stress conditions. Various regulatory elements and patterns are considered in relative chronological order. We also considered it necessary to pay attention to key high-performance methods for studying the dynamics of genetic information at the stage of translation.

Type III interferon (IFN-λs) exhibit potent antiviral activity and immunomodulatory effects in specific cells. Nucleotide fragements of bovine ifn-λ (boifn-λ) gene was synthetized after codon optimization. The boifn-λ gene was then amplified by splicing by overlap extension PCR (SOE PCR), resulting in serendipitous acquisition of the mutated boIFN-λ3V18M. Recombinant plasmids pPICZαA-boIFN-λ3/λ3V18M were constructed and the corresponding proteins were expressed in Pichia pastoris with high-level extracellular soluble form. Dominant expression strains of boIFN-λ3/λ3V18M were selected by Western blot and ELISA, cultured on a large scale, and the recombinant proteins purified by ammonium sulphate precipitation and ion exchange chromatography, yielding 1.5g/L and 0.3 g/L, with 85% and 92% purity, respectively. The antiviral activities of boIFN-λ3/λ3V18M exceeded 106 U/mg, were neutralized with IFN-λ3 polyclonal antibodies, were susceptible to trypsin, and retained stability within defined pH and temperature ranges. Furthermore, boIFN-λ3/λ3V18M exerted antiproliferative effects on MDBK cells without cytotoxicity at 104 U/mL. Overall, boIFN-λ3 and boIFN-λ3V18M did not differ substantially in biological activity, except for reduced glycosylation of the latter. Development of boIFN-λ3 and comparative evaluation with the mutant provide theoretical insights into antiviral mechanisms of boIFN-λs and provide material for therapeutic development.

Multipartite bacteria have one chromosome and one or more chromid. Chromids are believed to have properties that enhance genomic flexibility, making them a favored integration site for new genes. However, the mechanism by which chromosomes and chromids jointly contribute to this flexibility is not clear. To shed light on this, we analyzed the openness of chromosomes and chromids of the two bacteria, Vibrio and Pseudoalteromonas, both in the Enterobacterales order of gamma-proteobacteria, and compared it with monopartite genomes in the same order. We applied pangenome analysis, codon usage analysis and the HGTector software to detect horizontally transferred genes. Our findings suggest that the chromids of Vibrio and Pseudoalteromonas likely originated from two separate plasmid acquisition events. Bipartite genomes were found to be more open compared to monopartite. We found that the shell and cloud pangene categories drive the openness of bipartite genomes in Vibrio and Pseudoalteromonas. Based on this and our two recent studies, we propose a hypothesis that explains how chromids and the chromosome terminus region contribute to the genomic plasticity of bipartite genomes.

Stress is one of the important factors affecting the growth and development of plants. In recent years, a large body of data on transcriptional changes in response to stress in plants has been obtained. Despite the fact that the important role of the regulation of translation in response to stress has been proven in plants, knowledge in this area remains extremely scarce. In this review, we focused on mRNA translation in the cytoplasm of higher plants. Most of the current research on the effects of translation has been done in yeast and mammalian systems. Translation factors and mechanisms are mostly conserved among eukaryotes; however, some differences are known to exist among plants. A comprehensive understanding of the complex apparatus of translation and its regulation in plants is required. In this work, we have tried to update modern ideas about the regulation of translation under conditions of abiotic stress.

Cystic Fibrosis (CF) is an autosomal recessive genetic disease caused by mutations in the CFTR gene, coding for the CFTR chloride channel. About 10% of the CFTR gene mutations are "stop" mutations, which generate a Premature Termination Codon (PTC), thus synthesizing a truncated CFTR protein. A way to bypass PTC relies on ribosome readthrough, which is the ribosome’s capacity to skip a PTC, thus generating a full-length protein. “TRIDs” are molecules exerting ribosome readthrough; for some, the mechanism of action is still under debate. We investigate a possible mechanism of action (MOA) by which our recently synthesized TRIDs, namely NV848, NV914, and NV930, could exert their readthrough activity by in silico analysis and in vitro studies. Our results suggest a likely inhibition of FTSJ1, a tryptophan tRNA-specific 2’-O-methyltransferase.

Evolution of SARS-CoV-2 has followed similar trends as other RNA viruses, e.g., HIV-1 and influenza A. Rapid initial diversification was followed by strong competition and rapid succession of dominant variants. Host-initiated RNA editing has been the primary mechanism for introducing mutations. A significant number of mutations were detrimental and were quickly purged. Fixed mutations are mostly diversifying mutations selected for host adaptation and immune evasion, with the latter accounting for more of the changes. However, immune evasion often comes at the cost of functionality, so that optimal functionality is still far from being accomplished. Instead, selection for antibody-escaping variants and accumulation of near-neutral mutations has led to suboptimal codon usage and reduced replicative capacity as demonstrated in non-respiratory cell lines. Beneficial adaptation of the virus includes reduced infectivity in lung tissues and increased tropism for the upper airway, resulting in shorter incubation periods, milder diseases, and more efficient transmission between people.

We designed a novel growth controller regulated by feeding of an unnatural amino acid, Nε-benzyloxycarbonyl-L-lysine (ZK), using a specific incorporation system at a sense codon. This system is constructed by a pair of modified pyrrolisyl-tRNA synthetase (PylRS) and its cognate tRNA (tRNApyl). Although ZK is non-toxic for normal organisms, the growth of Escherichia coli carrying the ZK incorporation system was inhibited in a ZK concentration-dependent manner without causing rapid bacterial death, presumably due to generation of non-functional or toxic proteins. The extent of growth inhibition strongly depended on the anticodon sequence of the tRNApyl gene. Taking advantage of the low selectivity of PylRS for tRNApyl anticodons, we experimentally determined the most effective anticodon sequence among all 64 nucleotide sequences in the anticodon region of tRNApyl gene. The results suggest that the ZK-regulated growth controller is a simple, target-specific, environmental noise-resistant and titratable system. This technique may be applicable to a wide variety of organisms because the growth inhibitory effects are caused by “informational disturbance”, in which the highly conserved system for transmission of information from DNA to proteins is perturbed.

In addition to the canonical loss-of-function mutations, mutations in proteins may additionally result in gain-of-function through the binary activation of cryptic ‘structural capacitance elements’. Our previous bioinformatic analysis allowed us to propose a new mechanism of protein evolution - structural capacitance – that arises via the generation of new elements of microstructure upon mutations that cause a disorder-to-order (DO) transition in previously disordered regions of proteins. Here we propose that the DO transition is a necessary follow-on from expected early codon-anticodon and tRNA acceptor stem-amino acid usage, via the accumulation of structural capacitance elements - reservoirs of disorder in proteins. We develop this argument further to posit that structural capacitance is an inherent consequence of the evolution of the genetic code.

The monophyly of Nymphaeaceae (water lilies) represents a critical question in understanding the evolutionary history of early-diverging angiosperms. A recent plastid phylogenomic investigation claimed new evidence for the monophyly of Nymphaeaceae, but its results could not be verified from the available data. Moreover, preliminary gene-wise analyses of the same dataset provided partial support for the paraphyly of the family. The present investigation aims to re-assess the previous conclusion of the monophyly of Nymphaeaceae under the same dataset and to determine the congruence of the phylogenetic signal across different plastome genes and data partition strategies. To that end, phylogenetic tree inference is conducted on each of 78 protein-coding plastome genes, both individually and upon concatenation, and under four data partitioning schemes. Moreover, the possible effects of various sequence variability and homoplasy metrics on the inference of specific phylogenetic relationships are tested using multiple logistic regression. Differences in the variability of polymorphic sites across codon positions are assessed using parametric and non-parametric analysis of variance. The results of the phylogenetic reconstructions indicate considerable incongruence among the different gene trees as well as the data partitioning schemes. The results of the multiple logistic regression tests indicate that the fraction of polymorphic sites of codon position 3 has a significant effect on the recovery of the monophyly of Nymphaeaceae. Taken together, these results indicate that the monophyly of Nymphaeaceae currently remains indeterminate, and that specific phylogenetic conclusions are strongly dependent on the precise plastome gene, data partitioning scheme, and codon position evaluated. In closing, I discuss the importance of archiving all data of an investigation in publicly accessible data repositories, along with sufficient details to replicate the published results, and provide recommendations on future plastid phylogenomic investigations of Nymphaeales.

The SARS-CoV-2 polybasic furin cleavage site is still a missing link. Remarkably, the two arginine residues of this protease recognition site are encoded by the CGG codon, which is rare in Betacoronavirus. However, the arginine pair is common at viral furin cleavage sites, but are not CGG-CGG encoded. The question is: Is this genetic footprint unique to the SARS-CoV-2? To address the issue, using Perl scripts, here I dissect in detail the NCBI Virus database in order to report the arginine dimers of the Betacoronavirus proteins. The main result reveals that a group of Middle East respiratory syndrome-related coronavirus (MERS-CoV) (isolates: camel/Nigeria/NVx/2016, host: Camelus dromedarius) also have the CGG-CGG arginine pair in the spike protein polybasic furin cleavage region. In addition, CGG-CGG encoded arginine pairs were found in the orf1ab polyprotein from HKU9 and HKU14 Betacoronavirus, as well as, in the nucleocapsid phosphoprotein from few SARS-CoV-2 isolates. To quantify the probability of finding the arginine CGG-CGG codon pair in Betacoronavirus, the likelihood ratio (LR) and a Markov model were defined. In conclusion, it is highly unlikely to find this genetic marker in betacoronaviruses wildlife, but they are there. Collectively, results shed light on recombination as origin of the virus CGG-CGG arginine pair in the S1/S2 cleavage site.

A protocol was designed for plasmid curing using a novel counter-selectable marker, named pylSZK-pylT, in Escherichia coli. The pylSZK-pylT marker consists of the archaeal pyrrolysyl-tRNA synthetase (PylRS) and its cognate tRNA (tRNApyl) with modification, and incorporates an unnatural amino acid (Uaa), Nε-benzyloxycarbonyl-l-lysine (ZK), at a sense codon in ribosomally synthesized proteins, resulting in bacterial growth inhibition or killing. Plasmid curing is performed by exerting toxicity on pylSZK-pylT located on the target plasmid, and selecting only proliferative bacteria. All tested bacteria obtained using this protocol had lost the target plasmid (64/64), suggesting that plasmid curing was successful. Next, we attempted to exchange plasmids with the identical replication origin and an antibiotic resistance gene without plasmid curing using a modified protocol, assuming substitution of plasmids complementing genomic essential genes. All randomly selected bacteria after screening had only the substitute plasmid and no target plasmid (25/25), suggesting that plasmid exchange was also accomplished. Counter-selectable markers based on PylRS-tRNApyl, such as pylSZK-pylT, may be scalable in application due to their independence from the host genotype, applicability to a wide range of species, and high tunability due to the freedom of choice of target codons and Uaa’s to be incorporated.

The storage of biochemical information, which is a prerequisite for the development of the first cell, is an unsolved problem affecting all concepts of the origin of life. However, if the protected environment in the continental crust is taken into account, completely new possibilities emerge for identifying processes that may have been crucial for the formation of the first cell. Under this background, we can hypothesize that cellular life began, with a self-sustaining cycle of molecular reaction steps and information storage of peptide sequences in RNA in a crustal depth of approximately 1000 m. This cycle was made possible in an open system bound to gas-permeable tectonic fracture zones with a high proportion of CO₂ and/or N₂. It can be assumed that a large number of RNA-like molecular strands formed in the crustal environment, from which a special RNA was selected by flotation processes, which formed the basis of a proto-tRNA. The formation of peptides and vesicles in supercritical CO₂ and the chemical evolution of peptides have already been proven at conditions of the upper continental crust. The behavior of individual amino acids in connection with vesicle formation deserves special interest. Hydrophobic amino acids accumulate in the vesicle membrane, with their position in the membrane depending on the degree of hydrophobicity. Selection of a proto-tRNA with an acceptor arm ending with the bases CCA resulted in a distinctive property. The position of adenine at the tip of the acceptor arm permitted it to penetrate the membrane, allowing it to be linked to an amino acid at the 3'-OH position of the terminal ribose. The penetration depth was controlled by the hydrophobicity of the opposite anti-codon, with adenine always occupying the middle position for the hydrothermally formed hydrophobic amino acids. When the vesicle membrane was closely occupied by proto-tRNAs, the anti-codons acted as templates and stored the sequence of the peptides that form. In the cases of hydrophilic anti-codons, the acceptor arm does not reach far enough into the membrane. This allowed hydrophilic amino acids to be linked to 2´-OH.